dolphin
n.— «A huge floating crane was parked next to the Mukilteo ferry terminal Friday to repair damage done to the dolphins there. Dolphin is the term used to describe the large bumpers, sitting slightly out in the bay, which are used to guide the ferry into the terminal.» —“Huge crane performs surgery on a dolphin” by Pat Ratliff Mukilteo Beacon (Washington) Apr. 4, 2007. (source: Double-Tongued Dictionary)