We can swim and dive in water, sail and float on it, and so on. But we also use a whole lot of water all day. When you wake up, you take a shower. Then you have a nice breakfast with a cup of tea, and you also need to wash that cup after you are done. Then, before heading for school, you need to wash your hands and brush your teeth. Without even noticing it, you use a lot of water each day.
Even though we humans do not live in the sea, the sea is very important to us. We eat fish which are caught from the sea. Besides, salty sea water comes into contact with other bodies of water, such as salt pans, creeks and ponds. In that way, everyone comes in contact with sea water.