San Francisco Reef is one of the deeper reef sites off Avoca, sitting in about 30-35 m, and the Marine Life Network's Central Coast site list singles it out as having superior fish and sponge populations compared with the shallow Fifeshire Reef closer to shore. It is not one of the everyday commercial sites; it is more often dived by experienced locals and club members who want a deeper reef without the crowds of the ex-HMAS Adelaide. At this depth the reef changes character from the kelp-dominated inshore reefs.

Light is lower and swell surge is rarely felt, so sponges, sea whips, ascidians and gorgonian fans take over the rock, and the structure - ledges, boulders and low walls - is usually more colourful than on the shallower reefs. Fish congregate in bigger numbers: schools of yellowtail and silver sweep, bullseyes under the ledges, red morwong, and seasonal kingfish and samsonfish cruising the edges. Wobbegongs are common on the rock and sand edges, and in winter there is always a chance of grey nurse sharks moving between the deeper Terrigal reefs.

Published detail on the exact layout is thin, so treat the dive as an exploration: pick a direction along the reef, work it at a steady depth and turn in good time. With no-decompression limits short on air at 30 m-plus, nitrox extends the bottom time usefully. The site suits Deep or Advanced divers with recent experience who are comfortable descending a line in open water and managing their own ascent.

For divers who have done the Adelaide and Foggy Cave, it is one of several deeper Terrigal reefs - alongside Forresters Reef, The Pines and 5 Mile - that show what the Central Coast looks like beyond recreational training depths.

All boat dives in this area launch from the Terrigal Haven boat ramp at the southern end of Terrigal Beach, tucked behind The Skillion headland. From the Central Coast Highway follow Terrigal Drive into Terrigal, then Kurrawyba Avenue and Terrigal Esplanade to The Haven, where there is a paid car park beside the ramp; Pro Dive Central Coast's shop is a short walk away and gear is loaded on the ramp or the adjacent beach. Private boats need a ramp with good parking early on weekends as the car park fills by mid-morning in summer.

From The Haven the boat runs south past North Avoca to the waters off Avoca Beach, roughly 10 minutes. There is no published mark; the site is dived with local operators or club members who hold the GPS position.

Terrigal's offshore reefs are open to the Tasman Sea and are dived only when swell is below roughly 1.5 m; a north-east sea breeze building through the afternoon in summer and strong southerlies after a front are the usual reasons trips are cancelled, so morning departures are the norm. The Haven boat ramp is sheltered by The Skillion but the run out past the headland can be lumpy in a south-easterly. Visibility is best in late summer and autumn when the East Australian Current pushes warm blue water inshore, and worst after heavy rain when Terrigal Lagoon, Wamberal Lagoon and Avoca Lagoon open and stain the inshore water.

Winter water is cooler (around 15-17 °C) but often clear.

Descend the line directly to the reef at around 30 m, check computer no-deco limits early, and explore the sponge-covered ledges along a single direction before turning back on time or gas. Ascend the line with a safety stop at 5 m, or a longer stop if nitrox was not used.

Nitrox (EAN28-30) recommended to extend no-deco time; plan conservative ascents.

No regular scheduled trips; dived by Terrigal Underwater Group and occasionally by Pro Dive Central Coast on request for deep-qualified divers.