A submarine is a big boat that can go under the water.
It looks like a long, smooth tube. People can sit inside and steer it.
What a submarine can do:
- Swim on top of the water like a boat.
- Go down under the water to explore, like a little house that dives.
- Come back up to the top when it is finished.
How it goes down and up (easy idea): a submarine has special rooms that can fill with water and then be emptied. When those rooms fill with water, the submarine gets heavier and goes down. When the water is taken out, it gets lighter and floats up.
It also has a periscope, which is like a long mirror stick that lets people look above the water while the submarine is mostly under.
Fun, safe game to try with a grown-up: put a small waterproof toy in a plastic bottle and put the bottle in the bathtub. Press the bottle so a little water goes in and it sinks a bit, then lift it so it floats. This shows how submarines go up and down. Always play with an adult nearby.