阅读短文，根据短文内容回答问题

Water covers (覆盖) 70% of the Earth. Many fish and sea animals live in rivers, lakes, seas and oceans on the Earth.

In the oceans, you can find small beautiful animals—starfish (海星) and sea horses (海马).

You can find some big animals. Dolphins are big and clever. They love playing with people.

People also get food from the oceans. The seafood we eat is from the oceans. Fishermen use nets (网) to catch fish in the deep sea.

The oceans are important to all animals on the Earth. Animals get sick when the water is dirty. We must keep the oceans healthy.