Long Island Sound is a big body of water that's located between two places called Long Island and Connecticut. Think of it as a big swimming pool where people like to swim and fish. It's called "Long Island Sound" because it's surrounded by land on three sides and it's kind of shaped like a long rectangle.
The water in Long Island Sound comes from the Atlantic Ocean which is a very very very big body of water that's even bigger than Long Island Sound. When the ocean waves come into Long Island Sound, the water gets mixed up and becomes salty. But when it rains, the water in Long Island Sound gets less salty because the rain makes the water less salty.
There are many different kinds of animals that live in Long Island Sound. Some of them are fish, like the striped bass and bluefish. There are also big creatures like whales and dolphins that swim through Long Island Sound sometimes. And sometimes people even spot seals on the beaches! People who like to fish will usually go out on boats to catch fish in Long Island Sound.
In addition to being a fun place to swim and fish, Long Island Sound is also really important for the environment. It helps animals and plants to grow, and it's used to transport goods like oil, gas, and other things. So, it's kind of like a big part of nature that's really helpful to both people and wildlife!