Using Lasers To Find Submarines

Check out this story about how a scientist from the Naval Research Laboratory is investigating the use of lasers for finding or communicating with submerged submarines:

The shock wave created by either method can travel several miles and can be used for several purposes. One would be for one-way communication with underwater vessels. Triggering pressure waves in a specific order could allow a plane to communicate with underwater vessels via basic Morse code, or, more likely, says Jones, with a complex, encoded pattern of pulses.
Another use for laser-induced sound waves would be for mapping the ocean floor. When they hit a submerged object, the pressure waves bounce back. A nearby submarine or buoy could detect the pattern of those waves and create a map of the ocean floor, or the location of other submarines in the area.

Every once in a while, you read some story about how lasers are going to make submarines obsolete by making the ocean "transparent" and easily finding submarines. Somehow, these systems never end up working out. The reason, of course, if that you would get huge rates of false "positives" for any such system. One thing about ASW exercises that's always bugged me is how skimmers get a false sense of how good they are because they get cued to where the submarine is to start with -- otherwise, of course, it would turn such exercises into a waste of time because they'd never find the sub. Still, in the real world, they're not going to know where the subs are at to start their search, or even if one is there. When I was on the Carrier Group staff, during workups I saw many "positive submarine" detections called that weren't anywhere close to where the submarine actually was; in wartime, each of these would have likely resulted in wasted ordnance. Ships only carry so many ASW weapons. I think that to make skimmers aware of this, we should occasionally do ASW exercises where no submarine is present. That could be a valuable teaching lesson that could save ordnance for when it's actually needed during wartime.