SAN PEDRO, LOS ANGELES (KABC) --Cruise ships are floating cities at sea that carry thousands of passengers and crew - and could be at risk from potential terrorist attacks.
Keeping the giant ships safe from terrorists every time they visit Los Angeles is a monumental task.
It takes a collaborative effort by a team of law enforcement agencies, including the Los Angeles Port Police, U.S. Customs, the Coast Guard, federal air marshals and the cruise lines' own internal security forces.
"What we want to be able to do is to be in the background, but we also want to be noticed and that is the deterrent effect," said Michael Hillman, assistant chief with the LA Port Police.
There have been attacks before against cruise ships. In 1985, Palestinian terrorists took over the Italian cruise liner the Achille Lauro and murdered an American tourist in cold blood.
And even giant military ships docked at harbor are vulnerable. In 2000, al-Qaeda terrorists drove a small fiberglass boat filled with explosives right into the hull of the destroyer USS Cole while it was docked in Yemen, killing 17 sailors.
The cruise lines also have their own security forces. Before boarding the ship, you'll see security, heavily armed and on alert.
"Every person that comes on board, every item that comes on board is screened before it gets on board," said Wes Emory, with fleet security for Princess Cruises. "Either through X-ray, through explosives detection equipment or visual and manual search."
When boarding, every passenger is checked and then photographed. Preventing terrorists from storming the ship at sea is a top priority.
"Even Navy SEALS would have difficulty, unless they are coming from helicopter, getting on board a ship like this," Emory said.
Outside the ship, port police are constantly on alert that threats that may be targeting the hull.
"One threat that concerns us are small vessels that could do a Cole-style attack on a commercial vessel. And the other threat we're concerned with is underwater explosive devices," said Capt. Michael Graychik with the port police.
Dive teams go underwater, using high-powered flashlights to check for explosives that might be lurking in the water.
When the ship is ready to head out, the port police are on board the ship itself as well as in escort boats.
As the cruise liner hits the open water, an impressive well-choreographed transfer takes place.
Without slowing down, the side of the hull opens up, the port police jump off the cruise ship and onto the escort boat.
Now on the open water it becomes solely the responsibility of the cruise line to keep its passengers safe.