This is a Sherman DD preserved for a memorial in UK.
It was recovered from the Sea and mounted as a monument to the many Americans who lost their lives “invading” England.
The deaths were caused during a massive Amphibious landing exercise, when several of the landing craft were attacked by S boats. Ex Tiger involved the moving of some 3000 people to leave their homes, and resulted 900+ casualties. The attack didn’t stop the exercise.
Most casualties were caused by young inexperienced men, putting life preservers on the wrong way, during the panic. This caused them to flip headfirst in to the water when trying to swim, and the weight of the packs drowned them.
A great area of Slapton Sands were evacuated for the attack, and several houses including a hotle used for target practice. Theis was because the area looked just like Utah and Omaha beaches where the Amercias were going tobe attacking.
More here.
http://en.wikipedia.org/wiki/Exercise_Tiger