“Skin Diver Action! Jane Russell As you’ve never seen her before!” So declares the poster for 1955’s Underwater! , an adventure movie centered around the perils of deep-sea treasure hunters and the dangerous world they inhabit. And what a world it is! Our two intrepid leads spend their time navigating their boats into the waters where ships sank hundreds of years ago in hopes that they’ll be able to dive deep beneath the ocean surface, uncovering gold and riches untold among the wreckage of the past. This means they’re constantly contending with not only the dangers of the deep sea--including sharks, lack of oxygen, or becoming pinned beneath a piece of debris--but also the human threat of pirates and scavengers. Oh, and let’s not forget dynamite. Miles from the coast, it would seem that threats are everywhere.