In order to relax the nervous nerves, one day, Lake invited some friends to have a picnic on the beach. After a hearty meal, the young people held a bottle throwing competition. With a thump, the thrown bottles sank to the bottom of the sea one by one. However, the bottle that was thrown farthest did not sink, but shook with the bottleneck on the water.
It turned out that this was a funny behavior of a partner. The bottle he threw out contained half a bottle of wine. When friends were laughing at the bottle swinging from side to side, Lake was inspired by this accidental phenomenon: if the buoyancy of the upper part of the submarine can be increased, it will be stable and will not sink. When everyone wanted to punish the friend who broke the rules, Lake shook his hand excitedly and thanked him for doing himself a big favor.
Lake applied the principle of "the wine bottle is unsinkable" to submarine design, and invented a double-hull submarine hull composed of pressure-resistant shell and non-pressure-resistant shell, which achieved great success.