ocean floor
sea floor
ocean bottom
seabed
sea bottom
Davy Jones's locker
Davy Jones

Nearly all were sent to the bottom of the sea by the war's end.

We might have been alone together at the bottom of the sea.

They might have been on the bottom of the sea.

"What would happen if you sent them into the bottom of the sea?"

Then I'm going down to the bottom of the sea!

Both will be sent down to about 20 feet from the bottom of the sea.

They had found the rock at the bottom of the sea.

For this was a city on the bottom of the sea.

He built his base at the bottom of the sea.

It was like being at the bottom of the sea.