The Port of Grenville is defined by the water enclosed by a line from Telescope Point to Soubise Point to the nearest point on the mainland at Soubise. Grenville Bay, in position 12°7'N, 61°37'W, and St Andrew's Bay, separated by Marquis Islet, should not be entered without local knowledge. Breaking seas across the entrance to Grenville Bay will be experienced during strong north-east winds.

The port has a single pier with a depth alongside of 3.0 metres at its head. Vessels over 3.0 metres draught can anchor safely within the outer reefs, Pilotage is compulsory for all vessels over 150 grt. Pilots are based in St George's.