The Manly Gasworks dive takes its name from the gas plant that stood on Little Manly Point from 1883 until the 1960s, and its legacy is the strangest bottom on the harbour: the sandy-silty floor of the point is strewn with coal, from crushed fragments to lumps as big as a watermelon, spilled or dumped over eighty years of coal deliveries, now half-buried and colonised by weed. The site sits between Little Manly Cove and Spring Cove at the end of Stuart Street, a short walk from the Little Manly boat ramp where the Manly charters load, and it is entered over the rocks either from a rough track at the street's end or via the small bridge joining two concreted sections of foreshore. Depth is 4–5 m at the point and 6–7 m about 15–20 m out; the bottom is a sandy-silty mixture with small rocks, larger boulders in places, kelp patches and seagrass, and the shoreline has overhangs worth searching.

Michael McFadyen's verdict was that it is 'worth doing every now and again, and is probably a better night dive', and that is a fair description. Fish are small and numerous – old wives, bream, luderick, leatherjackets, yellowtail – with small cuttlefish and octopus under the ledges, a great many small rays on the sand, and the seahorses and pipefish that live along this whole stretch of North Harbour, inside the aquatic reserve. At night the coal beds come alive with crabs, shrimps and hunting cuttlefish.

The attraction is solitude: while Manly Cove and Shelly Beach are crowded, the point is empty, parking is free, and the walk is short. The drawbacks are the scrambly entry, ordinary visibility (4–5 m on most days) and the lack of any structure beyond the shoreline rocks. It suits Open Water divers who know the harbour, night-dive enthusiasts and photographers after rays and cephalopods, and it is easily combined with Little Manly Cove beach next door for a second, even easier dive.

From Manly Wharf follow East Esplanade south and then Stuart Street to its end at Little Manly Point Reserve (1.2 km; small free car parks in the reserve and at the bottom of Stuart Street, also the Little Manly boat ramp used by dive charters). Two entries: duck under the white fence at the very end of the street and take the rough track down to the water's edge (one ledge needs a hand with gear), or use the little bridge that joins two concreted sections and scramble over the rocks to a grassy area. Enter over rocks into 2–3 m.

Exit at the bridge, crawling up the exit slope, and walk back to the car park.

Little Manly Point faces south-east down North Harbour toward the Heads and is sheltered from the north-easter and most swell; a very large southerly swell reaching through the Heads puts surge on the rocks and makes the scramble entry unpleasant. Visibility is the constraint – normally 4–5 m, down to 1 m after rain, and up to 15 m on a rare winter flood tide. Any tide works but the rock entry is easier with water over the ledges.

Boat traffic to the Little Manly ramp and moorings in Spring Cove passes close, so stay near the shore and surface by the rocks.

Descend at the point in 4–5 m and follow the water's edge south-west into Spring Cove, zig-zagging between the shoreline overhangs and the sand at 6–7 m about 15–20 m out, over the beds of watermelon-sized coal lumps and crushed coal from the gasworks. Look under the overhangs for cuttlefish and octopus and on the sand for small rays. Turn at half air, return along the shore and surface at the bridge.

No operator runs it regularly; occasional Dive Centre Manly night dives and club dives. Mostly independent divers looking for a quiet alternative to Manly Cove.