When fishes swim nearby，you can catch them with your hands.If you have bottles of air on your back，you can stay in deep water for a long time.However，you can’t dive too deep，and you must be very careful when you dive in deep water. The deep sea is not an easy place to live in.It’s cold，and it’s dark，too.The deeper it is，the less sunlight there is.At about 3,000 feet，there is no light at all.It is very dark in the sea.Many fishes have no eyes.Some have big eyes.A few have eyes on one side.