How many times have you been swimming with weird fish in crystal-clear Caribbean waters, only to be forced to the surface by your stupid, inefficient lungs? SO many times, probably. James Bond never had that problem in Thunderball -- he used a sweet "rebreather" that allowed him to beat the tar out of aquatic henchmen indefinitely. Unfortunately, that kinda travel gear only exists in movies, right? Well, yes, but we're not that far off.