Bilgola is the small, steep-sided beach between Newport and Avalon, reached by the hairpin bends of The Serpentine and framed by headlands of cabbage-tree palms, and its northern headland offers a rock-platform dive onto a modest but pleasant reef. Vizzbud's description is of a rocky reef that 'slopes gently from 2 metres to sand around 12–15 metres, featuring scattered boulders and kelp gardens', rated intermediate for the entry rather than the diving, with an average depth of 8 m. It is one of the few documented shore entries on the stretch between Long Reef and Palm Beach.

The reef is typical of the exposed northern headlands: kelp on the shallow rock, boulders with undercuts as the slope steepens, and a sand line at 12–15 m where weedy sea dragons are found along the edge of the kelp. Wobbegongs and blue groper are the reliable large animals, red morwong and other reef fish are common, and cuttlefish and octopus are active at night, when Vizzbud suggests the site is at its best. Port Jackson sharks shelter under the boulders in winter and eagle rays cross the sand.

The difficulty is the platform. Bilgola's northern headland takes the north-easterly swell head-on: the rock is slippery, the entry crevices surge, and in anything above about a metre the exit becomes a problem with no good alternative but a surf exit onto the beach. Mid to high tide and a westerly morning are the conditions to wait for, and parking at the bottom of The Serpentine is scarce.

Bilgola suits experienced independent divers on the upper Northern Beaches wanting a reef with sea dragons close to home, and it is not a beginner's entry. Details are from Vizzbud and should be confirmed on site.

From Barrenjoey Road turn down The Serpentine, the winding road that drops to Bilgola Beach, and park at its terminus by the surf club (limited spaces, full early on weekends). Walk north along the sand and onto the rock platform at the northern headland – about 200 m. Enter from the platform on the top half of the tide; the reef slopes away to the east and north-east.

Exit at the platform between sets, or if it is awash, surface-swim back and exit through the shore break onto the beach.

The beaches between Narrabeen and Palm Beach face east to north-east and are open to the full Tasman swell; anything over about 1 m from the north-east or east makes the rock-platform entries a wash zone and puts surge across the shallow reefs, and a southerly swell wraps around the headlands. Choose mornings with under 1 m swell and a westerly or light north-easterly, on the top half of the tide so the platform edges are covered. Visibility is 5–12 m on winter westerlies and drops after rain when the lagoons open.

There is no dive shop north of Brookvale except Dive Spear and Sport at Mona Vale, so fills and advice are limited; these are independent divers' sites. Bilgola's northern headland is exposed to north-easterly swell, which makes the platform slippery, the entry rough and the exit options limited in larger seas; surge works through the entry crevices even on moderate days.

Enter off the northern platform, descend to 4–5 m and follow the reef north-east and east down through the boulders and kelp to the sand edge at 12–15 m, where sea dragons live along the margin; turn at half air and come back shallower along the reef to the platform, ascending in its lee.

No operator; independent local divers. Fills at Dive Spear and Sport, Mona Vale.