SAN DIEGO (AP) — While security has tightened at the U.S. border, drug smugglers are increasingly turning to the high seas.

The area where boats were seized off California and the northwest coast of Mexico tripled to a size comparable to the state of Montana during the 2013 fiscal year, which ended in September. Off South America, traffickers over the years have been traversing territory so big the continental United States could be dropped inside of it.

Mexico’s Sinaloa cartel has been loading marijuana bales onto 50-foot vessels as far south as the Mexican port of Mazatlan — where its leader, Joaquin “El Chapo” Guzman, was captured early Saturday — and running them up the Pacific coast to the U.S., deep into California. It’s unclear if Guzman’s arrest will hinder the maritime runs.

Meanwhile, budget cuts have hit one of the lead U.S. law enforcement agencies on international waters — the Coast Guard, the only U.S. military service able to make drug arrests hundreds of miles offshore. To meet automatic federal budget cuts, it reduced its operating costs by 25 percent in 2013. It also lost help from U.S. Navy ships on drug missions off Latin America that were decommissioned and not replaced because of cutbacks, or sent elsewhere because of Washington’s new military focus.

As such, only a third of suspected drug smuggling boats or aircraft out of South America that were tracked by U.S. intelligence in cocaine-trafficking corridors in the Pacific and Caribbean were stopped last year, the Coast Guard’s top officer, Adm. Robert Papp, told The Associated Press.

“Our interdictions are down 30 percent from the year before, when we had more assets out there, so that’s an indicator to me that as soon as we start pulling assets away, they’re running more drugs and they’re getting through,” Papp said.

U.S. authorities stopped some 194,000 pounds of cocaine last fiscal year — more than 40,000 pounds less than in 2012, according to Coast Guard statistics. Marijuana seizures dipped between 2012 and 2013 from 124,000 pounds to 81,000 pounds.

On Monday, authorities said they seized a 30-foot boat in the harbor in Oceanside, north of San Diego, with more than 500 pounds of methamphetamine inside a compartment. Customs and Border Protection said the twin-engine boat came from Mexico.

Defense officials have warned that the cuts would hamper efforts to reach the president’s goal of intercepting 40 percent of the illicit drug shipments flowing into the region by 2015. Fighting drug traffickers at sea is crucial because small aircraft used by traffickers can only carry about a ton of drugs versus large boats that can cart up to 20 tons of cocaine or more, authorities said.

As much as 20 percent of the cocaine moving through South America ends up in the United States. Large amounts also travel across the ocean into Africa, providing funding for insurgents and drug traffickers, and then on up into Europe.

“We’ve had to cut back in hours and funding, and cut back on resources on the water,” said Cmdr. Chris German, deputy chief of law enforcement for the 11th District, which stretches from Oregon to Peru. “The Coast Guard’s aircraft and ships have cut back on fuel, so every hour we’re not in the air or on the water, it does leave a gap.”

Even so, sea smuggling has not grabbed the attention of lawmakers like the flow of illegal goods across the land border, where billions have been spent on beefing up security. Part of the reason is the challenge to patrolling the ocean.

With more than 42,000 active-duty members, the Coast Guard is assisted in the drug war by other U.S. agencies.

It works closely with other nations, but that help only goes so far. Bilateral treaties sometimes limit waters it can patrol, and some of the foreign navies are small and underequipped.

U.S. officials, for instance, cannot venture into Mexican waters without prior permission and will stop a chase and alert Mexican authorities if suspected boats cross into that territory. Treaties with nations such as Colombia allow U.S. authorities more latitude.

“The land border is a much simpler border to defend. You can put up fences. You can put people out there. But it’s a finite area. You know where your land starts and where it ends,” Papp said. “When you go out into the maritime, it’s huge.”

The Coast Guard oversees 95,000 miles of coastline and 4.5 million square miles of maritime territory where the United States has rights: “We don’t have that many ships, and we don’t have that many aircraft, so there are many different places and routes that the bad guys can take to try and get around us.”

Rear Adm. Karl Schultz, the 11th District commander, said the tiny Coast Guard is doing its best to optimize its resources but the challenge is “like a police cruiser in Cleveland responding to something in Atlanta.”

Off California, smuggling vessels are typically spotted by planes from the Coast Guard or a federal agency, such as CBP, California National Guard or the Department of Defense. Coast Guard or CBP boats are then called to board suspicious vessels.

CBP is prohibited from firing on boats off the U.S. coast unless the pursuit begins within 12 miles of shore. The Coast Guard has no such constraints, so the onus has fallen on it as smugglers have ventured farther offshore.

The Sinaloa cartel has been loading marijuana bales vessels as far south as the Mexican port of Mazatlan and running them up northern Baja California after taking control of that state’s coastal territory several years ago, said Michael Carney, U.S. Immigration and Customs Enforcement’s assistant special agent in charge of investigations in San Diego.

Smugglers driving three-engine boats have been landing along remote coasts of Northern California, reaching as far as the beach town of Santa Cruz, which is about 350 nautical miles from the border city of San Diego. That’s a shift from the one-engine drug skiffs seen landing for years in San Diego County.

Support vessels carry fuel and supplies to go longer distances, and smugglers transfer loads onto U.S.-owned pleasure craft, believing they are less likely to raise suspicion than a foreign boat.

Last month, a Coast Guard C-130 plane circled 200 feet over drug runners who jettisoned plastic-wrapped marijuana bales off Mexico’s Baja California coast, about 175 miles south of the U.S. border. A Coast Guard inflatable boat closed in each time the three-engine vessel switched fuel tanks, according to Lt. Steven Davies, who monitored the hour-long, 30-mph chase from a nearby cutter.

By the time the four men were arrested, there were no drugs on board, but the Coast Guard fished 3,500 pounds of marijuana and 34 pounds of methamphetamine from the ocean.

Papp, speaking at a defense conference this month in San Diego, said that the Coast Guard’s resources to patrol the high seas and intercept threats are “woefully inadequate at this point.”

Its aging fleet of larger cutters is being replaced with faster, more capable National Security Cutters, but the number of high endurance cutters best suited for the high seas has dropped from a total of twelve to eight and will remain that way. The service’s operating budget will return to 2012 levels this year, but future years are uncertain.

Meanwhile, demands for the Coast Guard’s 240 cutters, some 1,775 boats, and about 200 aircraft are expanding with the warming arctic and its emerging fisheries, cruise ship routes and commercial traffic.

Rep. Eliot Engel, D-N.Y., has called for an evaluation of U.S. anti-narcotics efforts out of concern over the limited successes of the multibillion dollar war on drugs and wants more investment in prevention programs to curb the U.S. market for illegal drugs.

“Drug traffickers continue to find new ways to circumvent our laws,” Engel said. “Unfortunately, Congress’s draconian budget cuts have made the Coast Guard’s ability to collect intelligence on and interdict drug traffickers increasingly difficult.”

In 2013, the service lost one of its own to traffickers who rammed their 30-foot boat into the small craft of Chief Petty Officer Terrell Horne III, 34, near Santa Cruz Island off Los Angeles.

Horne’s death drove home the dangers of the war on drugs at sea, said Petty Officer 2nd Class William Pless, 28.

“You never know what you are going to encounter,” said Pless, his gun at his side as he looked into the gray mist hovering over the Pacific waters on a recent evening, miles from the Mexican border.