WHO: Jason Osborne, of Odessa, who scuba-dives across the country looking for ancient marine life. WHAT: A newly discovered genus and species of parasitic marine isopod, known as Calverteca osbornei, that lived 18 million years ago.WHY IT’S SO GREAT: It will shock no one that few explorers volunteer to scuba dive in mucky water. In near darkness, divers may suddenly encounter alligators, catfish with mouths as wide as your shoulders, or water snakes as big around as a forearm. They may find they’re surrounded by a large fishing net or a fallen tree. They may try to rise to the surface and realize (whoops) they’re in a cave. “I’ve been bumped by a bull shark in a river system in Virginia,” said Jason Osborne, a 53-year-old…