Cool Technology: Diver Suppression Systems

This is pretty cool. I wonder if the Navy is using these things at Navy Yards and Bases.

One of the more recent of the detection systems is the Cerberus360 swimmer detection system. This is a (large) refrigerator size device that is lowered to the ocean floor in the middle of the area you want to guard. Cerberus360 uses sonar to detect anything, large enough to be a threat, up to 800 meters out. Actually, during tests, it was able to detect an approaching underwater scuba swimmer at 900 meters. Cerberus360 works well in shallow water, and can be tweaked by the operator, once emplaced, to be even more accurate.

and

Al Qaeda groups are know to have bought scuba gear and trained for attacks like this, but none have been attempted yet. But last year, Raytheon Corporation got a patent for a sonar type device that can disable divers as well. The Raytheon "swimmer denial" uses sound waves that are tuned to cause severe gastric distress in humans. Makes you heave into your scuba mask. This makes further underwater operations difficult, if not impossible. However, Raytheon has not announced any timetable for the delivery of these systems.

That sounds quite effective to me. Though I wonder what it does to the local wild life. Sonar is known to screw up cetacean life, so these various systems aren't likely to be eco-friendly.