By John Biemer, Associated Press

ABOARD THE USS TYPHOON � The six men in blue uniforms strapped on bulletproof vests and loaded 9 mm Berettas. They piled into a rigid-hulled inflatable boat with two 60-horsepower engines and shoved off from a 170-foot Navy patrol cruiser.

Members of a Navy crew armed stations at machine guns, grenade launchers and a 25 mm cannon, ready to protect the Coast Guard crew on the rig, if needed, as they sped toward their target.

This isn't the Persian Gulf -- it's the Chesapeake Bay, in a scene repeated regularly by the Coast Guard as it girds for possible terrorist attacks.

The Sept. 11 attacks came by air. Federal agencies such as the Customs Service and Coast Guard have joined with state agencies to make sure a new wave does not come by sea.

Coast Guard patrols have intensified on major waterways. Police scrutinize boats anchored near major bridges. Naval vessels are given wider berths as they ply U.S. waters. Armed sea marshals board cruise ships and Coast Guard crews escort the ships safely into harbor.

At the Customs Service, drug-sniffing dogs and X-ray machines are joined by inspectors using portable radiation detectors the size of a pack of cigarettes to determine if cargo contains nuclear material. Searches begin at overseas ports before the shipments depart.

More than half the goods entering the United States arrive by oceangoing cargo containers. In 2001, the Customs Service processed more than 214,000 vessels and 5.7 million sea containers nationwide. Osama bin Laden and the al-Qaida network have vowed to cripple the U.S. economy. An attack using a sea container could be devastating to global trade.

Still, customs officials can't search through everything. "It's impossible -- it would grind the U.S. economy to a halt," said Kevin Bell, a Customs Service spokesman in Washington. So they rely on a risk-based strategy to target suspicious shipments.

A cargo ship coming to a U.S. port must give notice 96 hours before arrival -- up from a pre-Sept. 11 policy of 24 hours' notice. The ship reports its cargo, its destination and its previous ports of call, as well as the names of the crew and passengers, which are entered into security databases.

Coast Guard members go offshore to board and search cargo ships that raise suspicions by nature of their cargo -- or their crew. Some ships are not permitted to dock.

"The way we're looking at it right now is we safeguard life, property and critical infrastructure at sea and in all navigable U.S. ports and waterways," said Senior Chief Petty Officer Carolyn Cihelka, a spokeswoman for the Coast Guard Atlantic Area. "Whether that means responding to a terrorist threat or an urgent search and rescue case, that's our No. 1 mission."

In the days following Sept. 11, she concedes, there was a dramatic decrease in the Coast Guard's ability to conduct its traditional missions. Cutters that normally plied the Caribbean looking for drug smugglers were repositioned off the U.S. coast.

Now, the Coast Guard is learning to do it all -- with some help. For example, the USS Typhoon had recently carried Navy SEALs on missions throughout the Seven Seas. Now it's one of a dozen patrol-class vessels flying a Coast Guard flag and aiding boarding teams on both coasts and the Gulf of Mexico.

"We're stepping up our patrol to free them up to do that search and rescue," said Navy Lt. Robert Massaro, the captain of the Typhoon, as it escorts the Kara Sea -- a 608-foot tanker carrying gasoline, registered in Liberia, with a Russian crew -- into port.