Spider Cave and Bubble Cave sit within the same general cluster of features as the Looking Glass and Shark Gutters on Broughton Island's protected northern side, adding a genuine cave and cavern dimension to what is already one of the richest single dive areas on the NSW coast. Spider Cave is a low, tight cave that has been documented as a breeding site for grey nurse sharks — a significant finding given the species' critically endangered status and the importance of protecting any confirmed breeding or pupping habitat — and it also shelters a strong population of crayfish in its cracks and recesses. Its low profile demands careful buoyancy and a respectful, minimal-disturbance approach given both the ecological sensitivity of a breeding site and the practical risk of silting out a confined space.

Bubble Cave, close by, offers a different character: a larger chamber with a genuine internal air space, similar in concept to the celebrated air pockets at Fish Rock further north, where divers can surface briefly inside the rock, and it is also known to hold resident cod using the cave's shelter. Together the two caves give Broughton Island a genuine claim to being one of the most topographically varied dive locations in NSW — swim-through, wall, gutter, kelp bed and now true cave habitat all within a short boat ride of Nelson Bay. Divers should treat both caves with particular care given the ecological significance of Spider Cave as shark breeding habitat, following any specific guide instructions about approach distance and group size closely.

Boats depart Nelson Bay marina and run approximately 20 km/45-60 minutes north-east to Broughton Island, weather and vessel dependent. There is no facility or dive shop on the island itself; all diving is via day-trip charter from Nelson Bay, typically with two dives per trip around the island's northern and western sides depending on conditions.

Broughton Island sits fully exposed to ocean swell and is the first site cancelled when an easterly or north-easterly blow picks up; operators want well under 1.5 m swell and moderate wind to make the run worthwhile. The island's north side, where the grey nurse shark critical habitat sites (Looking Glass, Shark Gutters, North Rock) are found, gets some lee from a southerly, while other sides suit other wind directions, so skippers choose the exact site on the day. Visibility is best in autumn and winter, typically 10-25 m, and drops after rain from the mainland catchments.

Surge is common in the shallower features like Looking Glass and needs to be managed as a group.

Descend to around 12 m and approach Spider Cave low and carefully to avoid disturbing any breeding grey nurse sharks or the resident crayfish, then move to the nearby Bubble Cave, entering its larger chamber to find the internal air space and check for resident cod, before returning to the mooring.

Cavern-level comfort recommended given the confined nature of both features, even though they sit within recreational depth limits.

Let's Go Adventures (Nelson Bay) and Feet First Dive (Nelson Bay) both run daily boat trips to Broughton Island, weather permitting.