My guess is that Tom and his people were either entering or exiting a submarine. The guy on sonar duty on the boat probable either didn't know Tom's group were either coming or going and did a scheduled sonar ping to check the area for other boats and Tom was in the wrong place at the wrong time. I think the ping probable hurt him all over, because sonar is used to measure distance and size. Depending on how close he was to the boat when the ping came our, it may have messed with his nervous system and his head. But I'm just guessing this whole thing.