Hydra the Revenge (sometimes simply shortened to Hydra) is a steel Floorless Coaster at Dorney Park & Wildwater Kingdom in Allentown, Pennsylvania, United States. It is the only Floorless Coaster in Pennsylvania and was opened on May 7, 2005. Hydra was built on the site of the former wooden roller coaster Hercules, which was closed and demolished at the end of the park's 2003 season. Its name comes from the Greek Mythology story where Hercules battled the Hydra.