A Navy seal - actually a sea lion - took less than a minute to find a fake mine under a pier near San Francisco's AT&T Park.
A dolphin quickly located a terrorist lurking in the black water before another sea lion, using a device carried in its mouth, cuffed the pretend saboteur's ankle so authorities could reel him in.
The specially trained Navy Marine Mammals, based in San Diego, stole the show in a day of anti-terrorism training exercises held at ports throughout California.
More than 3,000 local, state and federal responders are participating in the scenarios that began Tuesday as part of California's annual, two-day homeland security and disaster preparedness exercises started by Gov. Arnold Schwarzenegger in 2004.
The drills include a fake attack on a container ship at the Port of Oakland, a bomb explosion at the Port of Redwood City, and terrorist attacks in waters off Los Angeles, Long Beach, Sacramento and San Diego.
California is home to 11 ports that handle 60 percent of the nation's container shipping traffic, said Tom LaPuzza, a spokesman for the Navy Marine Mammals program.
"Security is of vital importance,'' he said. "And humans are very slow in the water. Sea lions can see five times as well. And dolphins can use their sonar to spot items that would take humans days or weeks to find.''
The marine mammal programme is several decades old. LaPuzza said dolphins and sea lions were used during the Vietnam War and Operation Iraqi Freedom.
None of the animals have been harmed in the anti-terrorist work. They never have to carry potentially catastrophic mines.
Instead, they find the devices and place markers on them before Navy divers retrieve and defuse the devices.