Port Aransas -

As enforcement tightens on the border, smugglers are increasingly using coastal routes to get their contraband into the country, according to Customs and Border Protection authorities.

CBP?s The Office of Air and Marine combines both forces to keep an eye on U.S. waters using more than 360 Marine Agents and 200 vessels.

Marine agents patrol a watery border that extends into the Gulf of Mexico.

?There are vessels from all over the entire world here,? said Jason, a CBP Marine Agent who does not want his name used for security reasons.

The CBP Marine unit in Corpus Christie covers 241 miles of shoreline and includes one of the busiest commercial ports.

One recent evening, armed agents worked on board the ?Midnight Express.? On its website CPB refers to the 39-foot boat as ?the most powerful vessel used in law enforcement anywhere in the world.?

The boat has four 300 horsepower engines, can travel 250 miles round trip, and reach speeds of 63 miles per hour.

It?s been used to chase down smugglers. ?Like a car chase but on the water, and then we intercept them,? said CBP Marine Agent John, who did not want his last name used for security reasons. He recalled a boat chase that involved human smuggling.

The CBP Marine routes include open seas and small harbors and everything from small recreational boats to shrimp vessels and large freighters.

The Corpus Christi CBP Marine unit seized 440 pounds of cocaine worth $27 million and 3,000 pounds of marijuana valued at $7.6 million in 2011. But it?s not just drugs smuggled through these waters.

Marine Agent Alex, an agent who for security reasons does not want his full name used. He and other marine agents helped with a gun running case, ?They were automatic weapons. They were going down south.?

On a recent afternoon agents the agents jumped, went ashore to talk to some shrimpers, and docked in a small harbor near Aransas Pass. Shrimp season just ended in Texas, and the boats would soon leave for Louisiana.

?This has been known to have smuggling activity,? said Alex of the area.

As the sun set, the agents prepared for a long night ahead. Smugglers off the coast try to use the cover of darkness to sneak contraband across this watery border.

?The night time is generally pretty quiet time out here,? said Jason the Marine Agent guiding the Midnight Express. ?Therefore any vessels that are moving around are of interest to us.?