Whether it's to escape environmental collapse or to explore new, unknown territories, the drive to establish human colonies in places other than on Earth has been gaining momentum in recent years.
And while proposed bases on the Moon or Mars might get all the headlines, there's another equally hostile and largely unknown location a lot closer to home that explorers are looking towards: the bottom of the ocean.
This is by no means a new idea. Starting with French oceanographer Jacques Cousteau in the 1960s, people have been building and spending limited amounts of time in underwater habitats for decades.
