submarine

A submarine is an underwater vehicle that can carry people or goods. It's like a big metal tube that lets you breathe inside and move around while you're under the water.

When we say "submarine", usually we're talking about a real ship that can dive deep into the ocean, often to explore or for military use. But sometimes when someone says they're on a submarine ride or going submarine-ing, it means they're in a big glass-enclosed underwater vehicle designed for tourists. These are like big balls of clear plastic where you can look out at the fish and coral while floating down to the bottom of the ocean floor.