LOS ANGELES (AP) - The Coast Guard is seeking to protect the nation's ports from terrorist attacks by scuba divers with a sonar system so powerful it can distinguish swimmers from dolphins.
The security device, to be unveiled Wednesday, scans port waters and alerts authorities on land to any possible divers. A response boat then drops a second sonar below the surface for confirmation and sends back high-resolution images of the diver.
"Instead of alerting us to every sea lion, manatee or fish, this system will help us identify objects as a diver who just got lost or someone who intends on doing us harm," Coast Guard Lt. Cmdr. Alan Tubbs said Tuesday. "To date the Coast Guard's law enforcement has been mostly above water. This is just another capability."
Concerns about terrorist strikes by scuba divers were raised three years ago after the FBI announced it was investigating whether al-Qaida operatives took scuba training to help blow up ships at anchor, power plants, bridges, depots or other waterfront targets.
Tubbs declined to discuss in detail how the system differentiates humans from animals, how far away it can detect divers or how many were being used. Cost estimates for the system, developed by Coast Guard researchers over the last 2 1/2 years with outside technology, were also unavailable, he said.
The device would only be deployed periodically and could prove especially useful to inspect waters during major public events such as welcome ceremonies for military ships returning to port.
Randolph Hall, co-director for the Center for Homeland Security at the University of Southern California, said sonars have long been used aboard submarines but he was unaware of any with sufficient resolution to tell divers and other objects apart.
He added scuba divers could target ships with higher accuracy than a small explosive-laden boat like the one used in the USS Cole blast that killed 17 sailors in 2000.
"Small craft loaded with explosives ... are probably a bigger threat because it's easier to deploy a larger amount of explosives. But an underwater diver could put explosives at a more critical part of the ship," Hall said.