The First Frontier
noun - The First Frontier is the Planet Earth's oceans.
An ocean is a body of saline water that composes much of a planet's hydrosphere, occupying more than two-thirds of Earth's surface. On Earth, an ocean is one or all of the major divisions of the planet's World Ocean – which are, in descending order of area, the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean (or Antarctic Ocean), and Arctic Oceans. The word sea is often used interchangeably with "ocean" in American English but, strictly speaking, a sea is a body of saline water (generally a division of the World Ocean) that land partly or fully encloses.
The Final Frontier refers to outer space, especially from the perspective of space colonization. It was a description of space used in the opening narration of the science fiction TV series Star Trek. However, the Final Frontier can also refer to the oceans, especially from the perspective of ocean colonization.
The Final Frontier