Why don't they just stay at the bottom of the ocean?

Before the mid-20th century, little was known about the ocean bottom.

"Our son is finally coming back to us from the dark and cold bottom of the ocean," she wrote.

But by that time I was on the bottom of the ocean.

About half a minute in, a city can be seen at the bottom of the ocean.

Plus you'd put a few bad guys at the bottom of the ocean along the way.

The island is now shown to be at the bottom of the ocean.

"I saw them picked up off the ocean bottom myself."

They live at the bottom of the ocean, sometimes in holes.

A return to somewhere that I don't know about - the bottom of the ocean.