It's actually not a new program - the Navy's had marine mammal units for many years now. Long before "terrorism" was ever a buzzword. Of particular interest is the Mark-6 unit (MK-6 MMS) which is an antipersonnel unit. It makes a lot of sense if you think about it - a suicide diver with the right explosives could probably take out a small naval vessel. A ship's sonar probably can't distinguish a diver from any other underwater mammal. And even if it could, bullets are ineffective in the water. It's a significant vulnerability if you think about it.