What is the blue planet: earth’s final frontier? explain

The Blue Planet: Earth's last frontier is the oceans. Oceans cover 70% of the Earth surface, which is enormous compared to the land. Oceans are known to be the last frontier on earth because a large portion of the Earth (Oceans) remained unexplored and unknown. We have only explored less than 5% of the oceans. The ocean contains several different species, ranging from microscopic to the blue whale. The oceans remain as frontier because of its mystery in deep down oceans, which is less studied and explored.  

places of higher salinity. there are parts of the ocean where hardly any rain falls but warm dry winds cause lots of evaporation. this evaporation removes water – when water vapour rises into the atmosphere, it leaves the salt behind, so the salinity of the seawater increases. this causes the seawater to become denser.