I am conducting research for my Master Thesis. I am a historian focusing on a historic battle between a Navy airship and a German U-boat that occured just south of Key West on July 19, 1943. The airship was shot down. There is controversy about whether the 4 depth bombs were actually dropped. A weak explosion was felt by the survivors about 8 hours after the crash. By this time the Gulf Stream had carrier them approximately 36 to 44 miles away from the crash site. I theorize that the bombs sunk to the ocean bottom and then eventually exploded. I need assistance figuring out whether the shock wave eminating from a deep water explosion of 250 lbs of TNT in water 2,500 to 3,000 feet deep could travel far enough and still be strong enough to be felt by swimmers 36 to 44 miles away.