The "long-tailed shark" is a nuclear attack submarine of the US Navy. 1April, 963, went deep into the sea, and the hull broke and sank to the bottom of the sea due to poor welding. 129 people were all killed. After analyzing and judging the wreckage that sank to the bottom of the sea, it was found that the reason of sinking was that the submarine encountered strong internal waves when sailing in the water, and dragged it to the bottom of the sea, which could not bear the ultimate pressure and broke. This is the result of strong internal wave vertical force.