CGI Snake with multiple heads meets The Most Dangerous Game. If you took the Most Dangerous Game genre in which people hunt other people for sport (Of which the popular Hunger Games is derivative) and stuck it on a mysterious island that just happens to have a mythical Hydra on it then you get Hydra: The Lost Island. A sub par CGI monster movie with really bad dialogue and acting and some typical creature munching. 4 People are released on an island as prey for some rich millionaires who they must flee from while a giant Hydra is loose. They set up a few Rambo/Predator traps, but mainly just run around in the not too expensive forest talking in between Hydra kills. People die....and our hero finds the sword of Hercules in some fake lava inside a cave to slay the beast.....(Spoiler Alert) He doesn't kill it all the first time around just because someone decided they wanted the creature to get loose on the ship at the end. There is nothing special about this typical low budget monster movie.