Halley's Fish, Book, and Diving Bell
Edmond Halley is best known as the astronomer behind Halley's Comet. That comet (and others) had been spotted for millennia before Halley realized that there was one particular comet that seemed to return every 76(ish) years.
But aside from his work on the comet (which did not return during his lifetime), Halley was up to a lot of other interesting stuff. He convinced his friend Sir Isaac Newton to publish his Principia (and even paid for the printing process), he was a ship captain, and he invented a form of diving bell that allowed for extended stays underwater. Have a look at some of Halley's fascinating non-comet life in this five-minute video from Objectivity:
Note: Halley wasn't always right. He was a proponent of the Hollow Earth hypothesis. Oops.