They slice through the water with explosive power, the biggest, fastest, most dangerous gamefish in the sea - sailfish, swordfish, and queen of them all, marlin. For generations, men have lusted after these great swashbucklers - as trophies - especially the thousand-pound marlin known as "granders." Hemingway was a huge marlin fan, and memorialized the great fish in his classic, The Old Man and the Sea. But we know remarkably little about any of these superfish. They are almost impossible to study in the open ocean, an undertaking that becomes even harder as the fishing industry continues to decimate their populations and those of their prey. In an effort to unlock some of their secrets, dedicated marine biologist and award-winning underwater filmmaker Rick Rosenthal sets out on a personal quest to film the sword-wielding giants face-to-face in the deep blue waters of their world.