I changed the premise from outerspace to Atlantis, the lost continent.
There's a water sport called Underwater Rugby where the team plays entirely underwater with only snorkels, no oxygen tanks. So let's say that someone discovers Atlantis deep in the Atlantic and a business venture wants to put a base of operations down there. Wouldn't it be nice to have men who can live down there?
An excerpt is in the SCI FI folder:
THE DEVILS IN THE DEEP BLUE SEA