The answer I was looking for is - Mooring dolphins.
Definition - They are a man made marine structure that extends above water level and is not connected to the shore. They come in a variety of shapes sizes and materials they are made from. Structural dolphins help guide, berthing or mooring ships at ports, docks or jetties, often paired with docks or sea walls where they offer structural protection. They also help secure vessels during loading or unloading.
I found this interesting site that offers more information on construction and use.