I know that "under the sea" means someone is under the sea surface, which is equivalent to being submerged under water. If that's the case, are there any differences between "in the sea" and "under the sea"?

For example, a person is scuba diving. What is the difference between:

He is scuba diving under the sea


He is scuba diving in the sea

Another example:

The fish is in the sea


The fish is under the sea

One more example:

The submarine is under the sea


The submarine is in the sea

2 Answers 2


The only real difference is that someone swimming on the surface of the ocean is still in the sea, but they aren't under the sea.

  • 1
    And a boat on the surface of the ocean can be said to be at sea.
    – J.R.
    Commented Apr 22, 2017 at 17:24

Normally we use under the sea to refer to a great depth.

The bathysphere revolutionized the study of deep sea creatures. It could submerge to great depths, enabling scientists to view life under the sea.

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