He works as a captain of a submarine.

A nuclear submarine can travel underwater for a long time.

Creatures in the deep sea are living, adapted to its harsh environment.

This submarine is capable of underwater travel to the deep sea.

He traveled underwater in a submarine.

He loves diving and goes to the sea every weekend.

He loves to dive into the sea.

That is a possible solution.

The possibility of that plan succeeding is high.

He is the captain of that warship.