By Mark Potter, Correspondent, NBC News

TUCSON, ARIZ. – On a helicopter inspection tour above the rugged mountains and vast desert in southern Arizona, Commander Jeffrey Self of U.S. Customs and Border Protection reflected on how much security has improved along the U.S.-Mexican border during his long career.

"After the vehicle barriers were built, and with the checkpoints going up, we're experiencing zero [undocumented immigrant] drive-throughs in an area where we were having 30, 40, 50 in a 24-hour period," he said, pointing to miles of vehicle barriers placed in the desert along the frontier.

U.S. Border Patrol has greatly reduced the number of cars and trucks loaded with people and drugs driving across the desert from Mexico into the United States. That, Self explained, has freed agents to focus their attention on immigrant and drug smugglers who walk across the border.  In the meantime, he added, authorities have also greatly reduced the number of hiking trails used by smugglers.

"In Arizona we have been very successful in increasing border security," Self said. "Over the course of many years now we've been resourced with tactical infrastructure, technology and personnel and they've been employed in a fashion that's gotten us greater results."

While conceding there are still many areas where drug and immigrant smugglers cross illegally into the U.S. -- often on private ranch land -- Self argued the threat has decreased dramatically and will continue to do so.

Mark Potter/NBC News

The U.S. border vehicle barrier used by authorities to stop trucks and cars from crossing the Mexican border in southern Arizona.

As the national debate over comprehensive immigration reform plays out, the question looms: just how secure is the U.S. border with Mexico? The answer appears to be mixed, with definite improvements nationwide and a downward trend in illegal immigration in most places – especially in the cities. But there are some areas, in rural Arizona and Texas, where residents insist the border is neither secure nor safe.

Gary Thrasher, a veterinarian and rancher in southern Arizona near Bisbee, says the rural border area where he works is actually less safe now than it was years ago, because of an increase in the number of armed drug and immigrant smugglers.

When the federal government increased security in the border cities, he said, it had the negative effect of forcing the smugglers to move to the large rural areas.

"The border statistically is securer than ever.  That means nothing,” he said.  “That's like saying we fixed this whole bucket, except for this hole down here.  You know it's still not going to hold water."

U.S. officials: look to the numbers 

Homeland Security Secretary Janet Napolitano frequently travels to the Southwest border and has made appearances before Congress where she has touted the recent improvements in border security and argued for passage of a comprehensive immigration bill.

"Fewer people are trying to emigrate illegally into this country than in four decades,” she testified before a U.S. Senate committee earlier this year. “What I know is that apprehensions are low, because attempts are low. Drug seizures, contraband seizures, all the numbers that need to be up are up."

In the year 2000, agents along the length of the Southwest border reported detaining 1,643,679 immigrants for allegedly entering the country without proper documentation.  Twelve years later, in 2012, that number had plummeted to 356,873, a decrease of 78 percent.

"San Diego and the Mexican border used to be the most lawless, violent places across the face of the earth with thousands of cross-border migrants on a given day,” said retired Gen. Barry McCaffrey, the former head of the Office of National Drug Control Policy. “We put in triple fencing and adequate Border Patrol and Coast Guard and it stopped."

Ranchers: rural border areas not secure

Critics of the administration's position on border security, however, say that while the overall apprehension numbers are down, they don't fully reflect the reality in areas where smugglers and immigrants still routinely make the illegal crossing into the United States from Mexico.

NBC News

An NBC hidden camera captures footage of border-crossers hiking across private U.S. ranch land in southern Arizona during late March.

On a small ranch near the border in southwestern Arizona, a mother of several children spoke under the condition of anonymity.  She fears what she described as an increase in drug and immigrant smugglers crossing her land by day and night.

"You're still having to pack a gun everywhere with you and make sure your kids can't go outside to play unless you are watching them." she said.  "The border is not secure. The Border Patrol doesn't have a very strong presence out here."

Texas police: a rise in immigrant smuggling

In the small town of San Juan, Texas, a few miles north of the Mexican border, Police Chief Juan Gonzalez toured some of the human stash houses his officers recently uncovered. They had been used to hide immigrants from all over the world who were smuggled across the border into the United States.

Gonzalez says his department has never dealt with as many undocumented immigrants as it encounters now. 

"In the past three years we've seen an increase.  And it's not a steady increase, it's a massive increase," he said.  "Too many people are getting through.  We've got too many holes in the border and we don't have enough manpower to make sure we secure the border."

About 75 miles north of the border, in Falfurrias, Texas, Benny Martinez, the chief deputy of the Brooks County Sheriff's Office, says his area is also deeply affected by a recent rise in illegal immigration. 

“The trending is going up,” he said.  “It hasn’t gone down at all, not here.”

Last year, officials and ranchers there found the bodies of 129 immigrants who died in the harsh terrain, presumably after crossing the border illegally.  Dozens are still unidentified and are buried in a local cemetery.  Some of the metal markers on the graves read, "Unknown Female" and "Unknown Remains."  One says, simply, "Bones."

Martinez does not believe the U.S.-Mexican border is at all secure in South Texas, given the rise in illegal immigration in Brooks County. 

"It's steady and I don't think it's going to go down, it's not going to happen anytime soon," he said.

PHOTOS: Border patrol faces surge in rural Texas border crossings

Ranchers like Linda Vickers, who lives just north of a Border Patrol highway checkpoint near Falfurrias, said she regularly sees, and often photographs, illegal immigrants cutting across her land as they try to evade the agents. 

“I’m seeing groups of 10, groups of 20 and I’m seeing them more often,” she said.

When asked about Obama administration claims that the border is more secure now, Vickers said that while it appears to be true elsewhere in the country, it’s not the case where she lives. 

“In the state of Texas, in the Rio Grande Valley, the border is not secure and I don’t think you’ll find a person, a real person, to say it’s secure,” she said.

Border patrol: South Texas a problem area

In South Texas, in the Rio Grande Valley sector, immigrant apprehensions rose 65 percent from the years 2011 to 2012 -- from 59,243 to 97,762, according to U.S. Border Patrol -- bucking the national trend of falling immigration numbers. 

This year, statistics reveal the Rio Grande Valley apprehension numbers have climbed even further, rising 55 percent compared to this time in 2012. 

Federal agents believe it reflects a recent increase in people fleeing the poverty, drug gangs and violence in Central America.

Privately, some agents say that, despite their great success in making more apprehensions, thousands of immigrants crossing the border illegally in South Texas still slip past them.

A majority of people involved in the security debate agree that most of the U.S. cities along the border are now much safer than they used to be and have much lower crime rates, thanks to high fences, increased monitoring technology and thousands of Border Patrol and other federal agents deployed there.  

But McCaffrey says U.S. officials need to do more for the rural areas.

“You have to give the Border Patrol and Customs and Border Protection the dollars and the technology to protect the American frontier,” he said.  “We’ve got to do it.  We owe it to the American people.”

This story was originally published on Thu May 2, 2013 11:29 AM EDT

MALIBU, CALIF. -- On a starry night in the hills overlooking the Pacific Ocean north of Los Angeles, a two-man California National Guard special forces surveillance team sets up a sophisticated night scope. Their mission is to search the horizon and the waters below for an increasing number of Mexican drug traffickers offloading multi-ton loads of marijuana--and sometimes illegal immigrants--on remote U.S. beaches.

"These service members are the eyes and ears of federal law enforcement here," said Lt. Kara Siepmann, of the Guard's National Drug program. When asked about what specifically they are looking for, one of the surveillance team members said, "We're looking for blacked out vessels and any suspicious activity we can find, any unusual boats coming through the area." 

Used to smuggle drugs from Mexico, this panga boat was captured near Huntington Beach, Calif., in August 2011. The faces of the three men being arrested have been obscured at the request of the HSI.

The soldiers work quietly and in the dark, aware that the Mexican traffickers have their own spotters here watching out for U.S. law enforcement personnel. "They don't want to land where the National Guard or the Border Patrol are looking for them," said Siepmann.

Turning fishing boats into drug boats
In the last few years, law enforcement officials said they have seen a considerable spike in smugglers loading drugs or immigrants onto boats in Mexico's northern Baja Peninsula, then motoring north to offload their illegal cargo along a 300-mile-long stretch of California beaches, sometimes within sight of the many luxury homes on the coastline. 

Courtesy of HSI/ICE

Used to smuggle drugs from Mexico, this panga boat was found in California's Ventura County in January 2012.

Related: Debate rages over Mexico 'spillover violence' in U.S.

Federal agents said this is the latest smuggling technique employed by Mexico's notorious Sinaloa drug cartel, headed by that country's most-wanted criminal, Joaquin "El Chapo" Guzman. The boats are small, open-hulled commercial fishing boats called pangas, which are commonly found in the inshore waters of Mexico and Central America. 

With their low profiles, the pangas are hard to spot in open water, but they can carry a large payload. Sometimes these 30- to 40-foot boats will have as many as four outboard engines, allowing them to outrun most vessels used by the authorities.

"The trend is pretty much going straight up," said Lt. Stewart Sibert, the captain of the US Coast Guard Cutter Halibut, which patrols in search of Mexican smugglers near the California coast. 

"The past few months have been very busy for us," he said. "We caught more drugs in these past two months than in the past two years."

According to arrest statistics reported by U.S. Immigration and Customs Enforcement, or ICE, there were 183 known "events" in fiscal year 2011 along the California coast involving the maritime smuggling of drugs or immigrants, up considerably from the previous three years. During the first seven months of this fiscal year, there have already been 113 such events as the numbers climb even faster than last year.

"We're seeing four and five tons of drugs come in per run and we're seeing dozens of runs. It's almost one or two per week at this point," said Sibert.

A dangerous trade heading north
Law enforcement officials have argued the rise in maritime smuggling is a direct result of their crackdown on smuggling operations along the U.S. land border with Mexico. As they first interdicted smuggling boats headed for beaches in southernmost California, near San Diego, they began to see the traffickers moving farther north to drop off their loads, which are then distributed across the country.

Related: Patrolling 'smugglers' alley' by air along the Rio Grande

"As we stop them in one area, they’re trying to go around us. We're sort of leapfrogging up the coastline," said Sibert. Recently, an abandoned panga and a hidden marijuana stash were found near San Simeon, Calif., more than 300 miles from the Mexican border.

"They go far out to sea to try to evade interdiction efforts along the border," said Claude Arnold, the special agent in charge for ICE Homeland Security Investigations. "They typically go 100 miles out or farther due west, and then they come north," to reach the U.S. coastline.

While the panga boats are considered relatively stable when used for fishing in calm inshore waters, officials said, they can be quite dangerous in rougher waters offshore, especially if they are overloaded with drugs or illegal immigrants. The boats rarely have adequate safety equipment and authorities speculate that many may have been lost at sea, along with their passengers.

Courtesy of HSI/ICE

Used to smuggle drugs from Mexico, this panga boat was found on California's Leo Carrillo Beach in August 2011.

"It's a direct indication of these criminal smuggling organizations' complete disregard for human life. They are driven by profit and nothing else," said Troy Matthews, of the U.S. Border Patrol in San Diego. "You'll have somebody driving the ship who is not necessarily highly-trained. You'll have poorly maintained vehicles that will break down and subsequently they are loitering out at sea for days."

A border security threat
As they find more boats on the beaches and make more arrests, U.S. authorities are learning more about how the smuggling operation work, and the degree to which they are coordinated with land-based trafficking operations.

"We've seen some pangas that run directly up onto the beach and upload their cargo," said Sibert. "And then we've seen some that will come in and transfer their load to recreational boats that look less suspicious and try to run them directly into the marinas and yacht clubs."

Many times the panga boat operators will land at night on remote beaches near roads or a highway where they met by other members of the smuggling group. "There's usually an offloading team that will have a rental boxcar, U-Haul, or something of that nature to take the payload and transport it to a stash house where an organization begins the distribution process," said Arnold. 

A particular concern voiced by many U.S. authorities is the potential national security threat these boats and smugglers represent.  "They're just as willing to smuggle perhaps a weapon of mass destruction as they are a load of narcotics," warned Arnold.  "And they're just as willing to smuggle a terrorist as people coming here to work."  

To coordinate their interdiction efforts, federal, state and local law enforcement officials have formed a coastal-area task force. "As they adapt, we will adapt, and they'll continually try to find new ways to get contraband and people into the country, and we're going to be right there nipping at their heels," said Arnold.

Authorities conceded, however, that so far they are seeing no let-up in the Mexican maritime smuggling trade, and, in fact, are actually seeing bigger drug loads on boats now than in recent years.

"It's a huge challenge," said Matthews, from the U.S. Border Patrol. "It's an immense geographical area that we have to cover. There is not only single agency that can cover it by itself."

Pope Benedict XVI is on a state visit to Cuba this week hoping to highlight the role of the Roman Catholic Church on the Communist island, as well as making subtle push for change.

Benedict called for "renewal and hope, for the greater good of all Cubans," during a speech on Tuesday. "I have also prayed to the Virgin for the needs of those who suffer, of those who are deprived of freedom, those who are separated from their loved ones or who are undergoing times of difficulty."

But the Cuban government was quick to say that there "will not be political reform" in the country as a result of the pope's visit.

NBC News' Mark Potter is in Havana. He answered interesting reader questions about Benedict's visit earlier today.

Click below to replay the chat.

HAVANA, Cuba – At the historic San Francisco de Paula church, in a working-class neighborhood of Havana, Auxiliary Bishop Alfredo Petit recently walked the long hallways where priests, nuns and lay workers were busy caring for some of Cuba's elderly and infirm and also operating an orphanage. Outside the church is a sign welcoming the pope: "Bienvenido a Cuba Benedicto XVI."

Petit hopes during the pontiff's three-day visit to the island his messages will provide an important boost for the Cuban Catholic Church and perhaps even inspire some gradual changes in Cuban society.  "I don't know what the words will be, but I think they will suggest more respect for human dignity,” he said.

Since the Cuban revolution in 1959, the Catholic Church has struggled to raise its public profile here. For decades, under the Marxist government of Fidel Castro, the church was ostracized and believers were punished. The country was officially declared atheist until the government loosened that description in the 1990's.

But, with Fidel Castro out of power now and his younger brother, Raul, in charge, the church has become much more accepted by the government. Recently, Cuban Cardinal Jamie Ortega negotiated the release of more than 100 political prisoners, although he was criticized by human rights activists after most of the prisoners were sent into exile.

"The church has now been accepted as a legitimate and important interlocutor of the government on sensitive topics like freeing political prisoners, the conditions of those in prison, the treatment of dissidents," said Jorge Dominguez, a professor at Harvard University's Kennedy School of Government.  "This is a wholly unprecedented role for the Roman Catholic in Cuba for the past half century."

With funds and supplies donated from overseas, the church also provides much-needed social services now as the government struggles to reshape Cuba's troubled economy. Church-run food banks and retirement homes along with medicine distribution centers have become lifelines many of Cuba's extremely poor.

"It is very convenient for the government that the church will engage in activities providing for people in need," said Juan Clark, a Miami Dade College professor emeritus and an expert on the Cuban Church.

Still, tensions remain over the issues of religious and personal freedoms.

Last year, the church convinced state security to stop harassing the "Ladies in White," a church-based dissident group. However, two weekends ago, three-dozen members of the group were detained during a protest march in Havana. Ironically, 13 other dissidents who recently sought sanctuary in a Havana basilica were turned over by church officials to police, sparking accusations the church may have actually grown too close to Cuban leaders.

Pope Benedict is now urging Cuba to find new alternatives to Marxism – patiently and peacefully – as the Catholic Church maintains a delicate relationship with the Communist government here. 

The pope’s first stop on Monday will be Santiago de Cuba, the island's second city where he will celebrate a large open-air mass. On Tuesday, he visits the town of El Cobre, home to a tiny wooden statue of Our Lady of Charity, a symbol revered by all Cubans – Catholic and non-Catholic alike.

Later that day he flies to Havana for what is expected to be a meeting with both Raul and Fidel Castro. On Wednesday morning he will celebrate another mass in Havana before departing the country.

 By Mark Potter, NBC News

RIVIERA BEACH, Fla. — On a morning fishing trip to a reef near the South Florida coast, 13-year-old Ray Moody was having the time of his life as he reeled in an exotic-looking species.

"Hey, it's a parrotfish," he yelled. "It's blue, it's a slippery blue one."

Brad Houston/NBC News

Anthony Del Valle, 16, gets a turn at the helm of Rich Brochu's fishing boat.

Standing near him along the boat rail was 16-year-old Anthony Del Valle, who had also hooked one. Captain Rich Brochu offered encouragement and a quick angling lesson: "It looks like you may have something there. Yep, keep that rod tip up."

The weekend trip was part of an after-school fishing program that Brochu, a former police officer and construction company owner, started at his daughter's school in Boynton Beach six years ago to help kids from low-income areas experience the excitement of fishing. Since Brochu opened the Florida Fishing Academy, more than 4,000 students, ages 8 to 18, have signed on to learn the thrill of the catch.

"It's almost like playing a sport. You don't know what's on the other side; there's a kind of mystery to it," Brochu said. "If they catch a fish that's like 3 inches, it's the biggest smile. They love it."

Along with ocean conservation, catch-and-release fishing techniques, boating safety and first aid, Brochu also teaches the kids how to avoid peer pressure, the dangers of drug abuse and the advantages of keeping busy and off the street corners.

"All the kids benefit from activities like this. You know, it gives them something to look forward to," he said. "Obviously, we want to give them a choice in life and hopefully do something better with their life."

In a high school classroom recently, Brochu and Bob Cawood, another fishing captain who helps teach the program, planned to teach knot-tying, But first, they took a few moments to talk about the dangers of smoking.

"Cigarettes can cause mouth cancer. If you think that's true, raise your hands," they asked. Most hands went up. A short time later, the two men began teaching how to tie a clinch knot and made a game of it by insisting the students tie them behind their backs. The room erupted in noise and laughter as the students tried to see who could do it fastest.

Brad Houston/NBC News

Youngsters get a taste of the sea aboard Ray Brochu's fishing boat.

Excitement also broke out at gymnasium in Riviera Beach when elementary school students learned how to cast toward plastic fish scattered along the floor, and during foot races for which the children had to first put on life jackets correctly before running to the other side of the room.

A boating reward

For students in the program who stay in class, keep out of trouble and do some volunteer work, there is a special reward most of them would never have a chance to experience otherwise. At a dock in Riviera Beach is a colorfully painted 38-foot fishing boat that students can go out on to fish with Brochu and Cawood.

"Some of these kids have never been on a boat, never been on the beach. That's one of the goals, to get them out here," Brochu said.

Derrick Campbell, an instructor at Village Academy in Delray Beach, is convinced the fishing program and the promise of boating trips work to inspire good behavior.

"They're more disciplined. They don't act up," he said. "They know that there's something at the end of the rainbow."

Vickie Verzi, a single mother, wholeheartedly agrees. She believes the fishing program has been "the salvation" of her teenage son, Donnie, by keeping him engaged and away from troublemakers.

"It taught him how to fish," she said. "It gave him an interest in something that was good for him, and it gave him a direction in life."

Donnie now volunteers on the boat and is known among his friends as an accomplished angler.

Anthony Del Valle's mom, Tania Serrano, is also a fan of the program. "It's a new passion, and it keeps him busy," she said.

A shark-fishing trip is a particular source of pride for Anthony, and his mom couldn't be happier.

"A lot of people are like, 'wow, shark fishing?' and I'd rather have him out shark fishing than be hanging out with the sharks on the street."

For Anthony, the fishing boat not only gives him something to do; it also brings him a sense of inner peace.

"It gives me a second chance to do something I like and stay out of trouble," he said while cranking his fishing reel. "It just puts me in my own world."

Sharing the experience

The nonprofit Florida Fishing Academy program is paid for by donations, grants and fundraisers. Among the supporters is famed marine wildlife artist Guy Harvey, whose foundation wrote large checks to support the school and also supplied the colorful vinyl wrap that covers the boat hull.

"What a win, win, win situation," said Steve Stock, president of Guy Harvey Inc. "What a great sport this is, but way beyond that, if we can turn some of these kids' lives around, pretty good."

Brad Houston/NBC News

Janel Scholine and Nick Corzo, in the background, cast their lures.

During the recent weekend trip, 16-year-old Janel Scholine reeled in several fish and said she was thrilled to learn a new skill.

"I love it. It's awesome. I didn't know anything about fishing, and now I do," she said, beaming. In fact, Janel learned so much that she is now a volunteer instructor teaching as many as 50 children at a time an academy program called Angling For A Healthy Future.

Layne Reyka, also 16, says fishing with captains Brochu and Cawood is a lot of fun and matches his personality: "I'm very competitive, so it's definitely the pursuit and the hunt, whether it be a big fish or a small fish — preferably a big fish!"

For Brochu, the size and the success of the program are a surprise. His plan had been to work just with the kids at his daughter's school. Since then, he said, the Florida Fishing Academy has taught in 46 Palm Beach County schools.

"I set out for one goal, and that was to save one kid," he said. "Now it's one child at a time, and we've saved a lot."

The reward, he said, is in hearing from parents how well their kids are doing and in watching kids fully engaged in a sport he and Cawood love.

"Bob and I are both on their level. We just enjoy it. It's a great time sharing the experience with them. We're living the dream." he said. "Making a difference is more important to us than making money."

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EDINBURG, Texas – While flying an afternoon patrol along the twists and turns of the Rio Grande, Lt. Johnny Prince, a veteran pilot for the Texas Department of Public Safety, spotted something suspicious: "Look here, we got a raft, a raft right here." 

Below him, in the middle of the river which separates Mexico from the United States was a group of men frantically paddling back to the southern riverbank, their attempt to reach the American side thwarted by the helicopter patrol.

Prince said he suspected the men were a team of drug cartel scouts who were planning to search the U.S. side of the river to make sure there were no law enforcement officers nearby.  If they determined the area was clear, he explained, they would then signal others to sneak a load of narcotics across the river in a raft.

Mike Avila, the helicopter's tactical flight officer, said that this was happening near an area nicknamed "Smugglers' Alley," because of all the illicit activity here.  Well-worn trails and a narrowing of the river have made this area a favorite for Mexican drug traffickers.

‘That car's loaded to the gills’
Earlier that same day, Prince and Avila found themselves flying inland in hot pursuit of two vehicles –a car and a truck –loaded with Mexican marijuana.  As the vehicles sped through city streets on the American side of the river, Avila trained the helicopter’s high-powered camera on the fleeing smugglers and Prince called out their locations by radio to pursuing troopers on the ground.

Mark Potter / NBC News

Lt. Johnny Prince, the pilot on the right, and Mike Avila, the tactical flight officer on the left, patrol the Rio Grande in a helicopter looking for drug smugglers.

One of the drivers sped along the wrong side of the road, then he raced through an intersection, almost striking two cars with his pickup truck.  "Oh no, oh no," groaned Prince.  Avila described another close call as the driver raced through a school zone before crashing into a building: "He nearly struck two school buses."

In both cases, the drivers – a man and a woman – were apprehended and troopers seized loads of marijuana from both their vehicles. Even from the sky, the pilots could see that one of the cars was carrying a lot of drug bundles.  "That car's loaded to the gills," said Prince. 

Increased aggression along a ‘porous’ border
For the helicopter teams, chasing smugglers along the Rio Grande in South Texas is virtually a daily occurrence. Pilots say they've seen the Mexican traffickers pushing larger amounts of illicit drugs into the United States over the last few years and have watched them become more menacing toward law enforcement officers and U.S. citizens.

"I've been working along the border for 14 years and in those 14 years I've seen the level of aggression increase exponentially.  The sheer volume of narcotics that's being pumped into our border has risen," said Capt. Stacy Holland, of the Texas Department of Public Safety Aircraft Section.

It's not unusual, Holland said, for smugglers to take only a couple of minutes to move more than a ton of marijuana across the river, up the U.S. side of the riverbank and into a vehicle which then heads north. "Our border is very open, our border is very porous," he said.

The pilots said they are convinced traffickers are much more likely now than they were a few years ago to confront U.S. law enforcement officials.  "We have video of them carrying AK-47's and side arms during these operations and they are not afraid to use them," said Holland. 

While flying in his helicopter, Prince has more than once been eye to eye with smugglers on the ground upset with his presence above.  "I've seen guns pointed at me, long guns.  I've seen rocks thrown at us.  One of the things they do is use sling shots with ball bearings in them," he said.  "A ball bearing with a good slingshot can do damage to this helicopter and that's been done."

Another serious concern is for the safety of Texas troopers and U.S. Border Patrol agents who have to tangle with the traffickers on the ground.  A particularly dangerous scenario involves agents coming upon a large group of smugglers loading a car with illegal drugs on the U.S. side of the Rio Grande. 

"Usually there's only one or two officers that first arrive at the particular vehicle on the river and they are encountering 15 or 20 cartel members," said Prince.  "On the other side, you will see another 10 to 15 cartel members, and if you see them armed they are going to be trying to cover the guys on the U.S. side."

Splashdowns
A highly unusual technique used by Mexican smugglers to elude capture by American authorities involves them driving trucks loaded with drugs into the waters of the Rio Grande.  It happens after Border Patrol agents or Texas troopers spot a drug-laden vehicle on the U.S. side of the river and give chase. 

If the smugglers can't elude their pursuers – either by speeding up or by throwing spikes into the road to flatten the tires of the officers behind they – they will then head back to the same spot along the river where traffickers brought the drugs ashore after floating them across from Mexico.

"If the loads get compromised, they will drive around in the United States, in Texas here, until they get their recovery teams set up on the river, to return the drugs back to Mexico," said Prince. 

The Texas Department of Public Safety has shot numerous helicopter videos of Mexican smugglers paddling over to the American side of the river to await the arrival of the truck racing toward them.  When the truck reaches the riverbank, it keeps going – right into the water. 

Texas Dept. Of Public Safety / Texas Dept. of Public Safety

Photo taken of a "splashdown" taken by the Texas Department of Public Safety. Drug smugglers drove their truck back into the Rio Grande river to escape U.S. law enforcement.

"Bam! All units, we have a splashdown, a splashdown in the river," a pilot on one of the videos can be heard transmitting on the radio. 

Before the truck sinks, the driver climbs out through the window and the recovery teams move quickly to save as much of the drug load as possible, throwing the tightly-wrapped bales into rafts. 

"Ok, we've got rafts in the river, a bunch of people on the U.S. side; that thing is loaded," said a pilot watching from above in one video.  "Suspects are in the water, trying to unload the vehicle," said another pilot hovering over a different scene.

As soon as the rafts are filled with off-loaded drugs, the smugglers paddle back to the Mexican side of the river where they are safe from arrest by American authorities.  Sometimes, the traffickers are so brazen they will make obscene hand gestures toward U.S. agents watching from across the river, or from above in helicopters.

The agents' only recourse at that moment is to notify Mexican authorities and hope they arrive in time to apprehend the smugglers.  Or, they can hope to catch the loads of drugs next time, when inevitably they are floated back across the Rio Grande during another smuggling attempt – sometimes on the very same day the drugs are recovered after a splashdown.

No end in sight
The pilots who routinely fly along the Rio Grande said they see nothing that would suggest there is any let up in the amount of smuggling along the river.  In fact, they predict increased violence on U.S. soil.

"You get a lot more home invasions, a lot of crook on crook crimes, a lot of kidnappings, the cartels coming over here maybe trying to collect money and then retreating back over to Mexico," said Holland. 

Texas newspapers have reported recently on cartel shoot-outs in Houston and McAllen, the wounding of a deputy, the arrests of alleged cartel leaders in the Rio Grande Valley and the seizure of cartel property in the U.S.—along with the almost daily news of major drug seizures.

Statements by the Obama Administration and by some local officials that the U.S.-Mexican border is safer than ever are derided by many of the pilots.

"Our citizens in our border towns are caught in the crossfire, and I mean that in the most literal sense sometimes," said Holland.  "It's important that our citizens, not only in the state (of Texas), but in the United States are aware of how porous our border is and what the threats are, and could be."

More coverage from Mark Potter: Along Mexican border, US ranchers say they live in fear

See more of Mark Potter's reporting on NBC's Nightly News with Brian Williams Tuesday evening.