The oceans are home to far more plants and animals than the land. We draw a rich harvest from the oceans. Seafood provides vital protein to millions of people. We get important products from kelp and other sea plants. Algae, or seaweed, is found in a lot of products that you use around your home every day.
Wind is the most common cause of surface waves.
There is only really one big ocean. Ocean water is salty because salt is a mineral that is found in soil and rocks. Flowing water picks up some salt and carries it to rivers. Rivers carry it to seas.