Shayleen Mills and her family are vacationing at the the seaside resort of Wildwood, New Jersey, along with hundres of other families. But there's something lurking in the water - something hideous from the depths of the sea. When Shayleen spots a jellyfish on the beach she doesn't think much of it. However, when a jellfish rises into the air and attacks, she knows she's in a lot of trouble. Soon, the resort community is under attack by horrify, glowing jellyfish. Shayleen and her two friends find themselves trapped in an amusement park, surrounded by dozens of electrified, vicious creatures. It's a vacation Shayleen will never forget - that is, if she makes it out alive!