Oil has been discovered under the North Sea.

He enjoyed a new life under the sea.

Although most islands in the ocean have been mapped, the ocean floor is generally unknown.

The ship touched ground.

The ship sank to the bottom of the sea.

They have climbed the highest mountains and walked on the floor of the seas.

Marine plants grow on the sea bed.

The divers found a wreck on the sea-bed.

It was found at the bottom of the river.

The new Mario game is an underwater adventure where he solves the mystery of an ancient kingdom sunk to the bottom of the sea.