It won't stop, because under the action of gravity, the watch will sink to the bottom of the sea until it reaches the bottom of the sea.

So far, there are two understandings. One is whether the hands of the watch will stop, and the other is whether it will stop sinking into the sea. Because of the fixed thinking, I subconsciously think it is the first case when I see the watch. Understanding the word "stop" is the key to this brain teaser.

Extended data:

Brainstorming originated in ancient India. It means that when thinking encounters special obstacles, you should quickly leave the habit of thinking and think about the problem from other aspects. Now refers to some intellectual questions that can't be answered by the usual way of thinking.

Brainstorming covers a wide range: educational, funny, mathematical, adult and so on. Brainstorming is a kind of entertainment and a popular word game.

Source: Baidu Encyclopedia-Brainstorming