Foggy's Cave is the signature deep dive of the Terrigal reef network and one of the most reliable grey nurse shark encounters on the NSW Central Coast. The reef drops from about 32 m to 36 m at its edge before a straight wall continues to 39 m, where a large boulder anchors a mooring; the cave itself is cut roughly 15 m into the underwater cliff face, about 10 m wide for most of its length but low — perhaps only 2 m high in places — with a floor thick with fine sand that demands careful buoyancy to avoid a instant whiteout. The cave sits in the corner where the main reef wall changes direction from a south-north to a west-east orientation, giving the site a distinct three-dimensional structure beyond a simple wall profile.The reason divers travel specifically for Foggy's Cave is the grey nurse sharks that regularly aggregate here, using the cave and surrounding reef as a resting and gathering point; despite their fearsome appearance, grey nurse sharks are docile, and a calm, non-intrusive approach typically allows for extended, close observation.

Beyond the sharks, the cave roof carries gorgonian growth and the walls support prolific, colourful sponge life, with eastern blue devils, luderick, red morwong and large black reef leatherjackets holding tight against the rock. Because the site sits at 32-39 m, it pushes at the edge of recreational no-decompression limits and some operators run it as a planned decompression dive, so this is firmly a deep-diving-experienced destination rather than an entry-level Advanced Open Water outing. Combined with the shallower Foggy Fish section of the same reef, Foggy's Cave anchors one of the best two-tank charter days on the Central Coast.

Boats depart Terrigal Haven and run a few kilometres north to Foggy Reef; Pro Dive Central Coast and Central Coast Divers include it in their charter rotation, and it is a favoured Terrigal Underwater Group destination given its grey nurse shark reputation.

Terrigal Haven and the boats launching from it are reasonably sheltered by The Skillion headland, but the reefs and wrecks further offshore are exposed to swell from the north-east through south-east; charters generally want under about 1.5 m swell and moderate winds. Visibility improves markedly when the East Australian Current pushes warm water down the coast, typically strongest from late summer into autumn, and drops after prolonged onshore wind or heavy rain feeds sediment out of the Terrigal Lagoon and nearby catchments. Winter brings cooler, sometimes clearer water and the best chance of grey nurse shark sightings at Foggy Reef.

This is a decompression-capable deep dive for most divers' no-decompression limits, so a stable weather window matters and bottom time must be planned conservatively.

Descend the mooring/shot line to the boulder at the base of the wall around 36-39 m, move into the cave entrance in the corner where the wall changes direction, checking the roof for gorgonians and the interior for grey nurse sharks holding in the sand-floored chamber, then ascend back along the wall for a staged safety stop given the depth.

Often run near or beyond recreational no-decompression limits at 33-39 m; nitrox recommended; some club/technical divers plan a short staged deco hang.

Pro Dive Central Coast (Terrigal Haven) and Central Coast Divers run regular boat charters to the Terrigal reef network; Terrigal Underwater Group club members dive the full spread of sites from private and club boats.