The main bay, also known as Koddiyar Bay, is located in the south and southeastern side and fairly regularly shaped, as well as enclosed and deep, forming a large natural harbour in the shores of the Indian Ocean.

The commercial harbour is located in the 5 km (3 mi) long and 4 km (2 mi) wide northern indentation, also known as China Bay, on whose western side lies China Bay Airport.

[3] The bay is overlooked by terraced hills in the northwest and its entrance is guarded by two headlands.

The latter two are wildlife sanctuaries[6] Trincomalee Harbour, formerly a naval base of the Royal Navy, was taken over by the Sri Lankan Government in 1956 to be developed as a commercial port.

The base in Trincomalee was fitted out to perform slipway repairs for the Sri Lanka Navy.