Quote Originally Posted by Didz View Post
Of course something like a river or marsh could simple swallow roundshot completely if they landed in it, although Nelson is supposed to have developed a technique for getting roundshot to bounce over water (not really very plausible, but its a story that persists).
The version I know of has to do with the US Navy, not the RN. The early USN is supposed to have used the idea to counter RN superiority in gunnery. I believe the aim was to use a low-trajectory shot, skip it once and hit the enemy ship at or below the water line.

It is actually very plausible. The principle is the same as skipping stones on water. While water will swallow any slow moving object, high speed is a different matter.