The harbour is divided into four major inner harbours by various piers and breakwaters. In the south west corner the Old Harbour (sometimes termed the inner Coal Harbour) is enclosed by the Old Pier constructed in 1767. 

The Old Harbour incorporates tidal public slipway. The exit from the Old Harbour leads to the Coal Harbour, bounded by the Traders Wharf which possesses a non-tidal public slipway. 

The Coal Harbour leads past the Marina Harbour which was created around 2001 together with the Western Breakwater and Eastern Breakwater to protect smaller boats. The Main Harbour covers the sweep from the Northern and Eastern breakwaters which mark a broadly North north east direction road past the harbour entrance and including all of the eastern part of the Harbour including St. Michael's Pier and Carlisle Pier and the five ship berths.