Abstract: Described is an apparatus for securing a boat to a dock or other marine structure that moves with the boat as the boat is raised and lowered by waves or the tide. The apparatus is secured to a dock or other marine structure and includes a track, preferably in a shape similar to that of an “I” beam, a carriage that moves along the track, and a bumper that is attached to a front portion of the carriage. The boat is secured to either a mooring line or mooring cleat on the carriage. As the boat is raised or lowered by waves or the tide, the carriage is also raised or lowered along the track accordingly. The bumper is secured to the outside of the carriage and prevents the boat from being damaged if the boat collides with the bumper.