Answer:
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.