Why are oceans called the last frontier? They cover three quarters of the planet; play host to thousands of species; and have a critical role in controlling the weather. And yet, scientific research has barely skimmed the surface of the world’s oceans. In fact, we know more about space than we do about the oceans. That is because the high water pressure deep below makes travelling under water difficult. Also, if the transportation device is not hard enough, you would get crushed.