A dolphin is a man-made marine structure that extends above the water level and is not connected to shore.
Dolphins are usually installed to provide a fixed structure when it would be impractical to extend the shore to provide a dry access facility. Typical uses include extending a berth (a berthing dolphin) or providing a point to moor to (a mooring dolphin). Dolphins are also used to display regulatory information like speed limits etc, other information like advertising or directions and navigation information like a daybeacon as well as ranges and lighted aids to navigation.
Funnily, a structure like this is known here as a “duc d’Albe”. It is said to be named after the duke of Alba (Il duca d’Alba), a Spanish army commander who is supposed to be the fist to have used a structure like this in the battles against the Netherlands during the 1570’s.
The Harbour Round Trip Collection:
A Misty View: