Submarine

A submarine is a kind of boat that can travel underwater. It looks like a regular boat, but it has a tall, round shape on top which helps it to stay underwater. The submarine is able to stay underwater for long periods of time without needing to come up for air, because it is filled with special air tanks that can store air to breathe. It also has a lot of special instruments and engines, which help it to travel quickly through the ocean. Submarines usually carry a crew of sailors, who take turns piloting the ship and helping to maintain it while they are underwater.