Okay kiddo, so you know how there are big boats called ships that people can ride on in the water? Sometimes these ships get old or they break and they can't be used anymore. When that happens, people might decide to sink the ship on purpose so that it stays in one place underwater.
Why would someone do that? Well, some people like to go scuba diving and explore things underwater - it's like exploring a secret world! And if there's an old ship down there to explore, that makes it even more fun. So people sink the ships on purpose to create something interesting for people to explore.
But wait, if the ship sinks, won't it hurt the animals that live in the water? Don't worry, kiddo, the people who sink the ships make sure that they don't hurt any animals. They clean the ship really well and take out anything that could be harmful to the animals before they sink it.
So, when people want to go scuba diving and explore the underwater world, they can now go to the spot where the ship was sunk and see all sorts of cool things like the underwater rooms and furniture. Plus, they get to see all of the fish and other animals that live in and around the sunken ship. Isn't that neat?