According to Sea Lions Alex and Zachary Guard U.S. Ships, the Navy is using sea lions to catch suspicious swimmers and divers near ships:
The sea lions have been trained to carry a special clamp in their mouths which they can attach to a suspicious person, Commander John Wood, Special Operations Officer Naval Forces Central Command, told Reuters.The clamp is attached by a line to a flotation device which marks the swimmer for security personnel to apprehend him. Wood would not explain in detail how the clamp worked or what would stop a swimmer removing it.
I don’t know why, but that clamp scares me. Anyway, I don’t normally think of sea lions as deep divers, but:
The mammals can dive to 1,000 feet, swim at speeds up to 25 miles per hour, as well as see and hear better under water than any human or mechanical device the military has.