The harbormasters at Greenwich Harbor are responsible for maintaining and supervising the use of the harbors and navigable waterways under the direction of the transportation commissioner.
Four marinas in Greenwich Harbor are available to residents from April to November, and they also provide winter storage. Byram Marina has about 300 slips that serve vessels to 7 meters (23 feet) long with 2.7 meter (9 foot) beam. It also offers out-water mooring for about 100 vessels of 11 meters (36 feet) with 2.1 meter (7 foot) draft.
Greenwich Harbor's Grass Island Marina can accommodate about 150 vessels and has some rack storage for kayaks and canoes. It offers out-water mooring for about 75 vessels. Greenwich Point Marina can accommodate about 260 vessels to 11 meters (36 feet) long with 2.1 meter (7 foot) draft. The Cos Cob Marina in Greenwich Harbor has about 300 slips for vessels to 7 meters (23 feet) long with 2.7 meter (9 foot) beam. It also offers storage for kayaks and canoes.
There is a commercial wharf in Greenwich Harbor owned by the Champion Energy Corporation, although it is not used today for its original purpose. It is leased to a recreational marina today. In the past, this Greenwich Harbor wharf received petroleum products by barge and tanker. The wharf has berthing space of almost 46 meters (150 feet) with alongside depth of 3.7 meters (12 feet) MLW.