Norwegian company Defense & Security Group (DSG) has developed a line of ammunition that can be fired into water or from underwater to above the surface without changing its trajectory.
Our friend David Crane at Defense Review has written an extensive article about the Supercavitating round …
With DSG Technology’s MEA Supercavitating Rifle Ammo, you can fire at an underwater enemy target from above the water, an above-the-water enemy target from below the surface, or at an underwater target while you are also underwater. For example, a U.S. Navy SEAL diver can perform an underwater approach on an enemy vessel and engage targets of opportunity while he’s still submerged several meters underwater. The only caveat is that he’ll have to compensate for optical refraction to hit the target. The same thing goes for engaging underwater targets from above the water.
The bullet design is scalable, so they could potentially build a underwater 30mm or 127mm cannon for anti-torpedo or submarine use.
[ Many thanks to JTolliver for emailing me the link. ]