Saw a show called Drain the Ocean a few months back that showed the US tanks that sunk in formation on D-Day (27 of 29 sunk). They are sitting on the bottom in an almost perfect formation pointed at the beach. The skirts they used to make them float were not tall enough and they were swamped and sunk.

Interesting the Brits and Canadians figured that out and launched closer to the beach but either the info didn't get shared or someone's ego got in the way of good decision making. How many lives could have been saved on Omaha if 29 rather than 2 tanks had made it onshore?