Look at a photograph of the earth taken by a satellite from space. It will show that a large part of the earth is covered with seas. The sea helps all forms of life on earth.
It is because the sea is the source of all the water they use. The sea is full of many forms of life, minerals, and salts.
It provides us with many kinds of fish, lobsters, corals, prawn and sea plants.
In some countries, people distill seawater and get fresh water. The sea is used as a road to transport goods and passengers from country to country. A large number of ships that carry containers, cross the seas every day.