Jellyfish invasion

Let's join a mystic adventurous world! The citizens of small island called "Pleasure" could be the happiest people in the world. But one day the fairytale has become a disaster. Strange jellyfish have appeared in the sea. People were frightened: sailors couldn't go to the sea, citizens were not able to swim. But courageous Jack decided to save his hometown! And he needs you! Help the captain to clear the way to the sea and find a key to the riddle!