The Bubble Cave is a popular Black Rock dive because of its air pocket. Exhaled bubbles from divers collect in the roof of a cave at about 13 m, and a group of three or four divers can put their heads into the air space. The Marine Life Network places it on the north-western corner of Black Rock, close to the boat ramp. McFadyen describes a route that takes in several features: descend to a wall, follow it to the left to a ridge that can be passed over or around, then cross sand and rubble into an amphitheatre-like formation at about 15 m where the cave opens.

Beyond the cave, a sandy gutter runs almost north–south for 30–40 m and reaches 21 m at its southern end, where a second cave runs right back into Black Rock. The return leg crosses sand and rubble and another ridge. The rock is covered in sponges, sea squirts, yellow zoanthids and gorgonians, and McFadyen notes good fish life, with blue groper, silver sweep, yellowtail, eastern blue devilfish and wobbegongs among the regulars.

The air in the pocket is exhaled gas and may be low in oxygen and high in carbon dioxide, so keep your regulator in. The dive suits Open Water divers who are comfortable in an overhead environment with an easy exit. Several other NSW sites share the name, including one at Montague Island, so specify Black Rock when booking. The sandy gutter is also a good place to look for rays and flathead on the way back to the boat.

Boat access only. Black Rock lies just off Lilli Pilli on the southern shore of Batemans Bay; the nearest ramp is at Mosquito Bay (Lilli Pilli), a couple of minutes' run, and Beneath the Bay brings divers from the Hanging Rock ramp in Batemans Bay in about 15 minutes. McFadyen notes it is only a couple of minutes' run from the ramp.

Anchor in 15–18 m off the north-western corner of Black Rock and follow the wall to the amphitheatre.

Like the rest of Black Rock, it is sheltered from southerly swell and is diveable on most days, but strong easterly or north-easterly swell makes the cave and shallow approach surge. Visibility drops after heavy rain when the Clyde River pushes brown water into the bay. The sand in the cave and gutters silts easily.

Descend to the wall, follow it left to a ridge, go over or around it and cross the sand and rubble to the amphitheatre at 15 m. Enter the Bubble Cave (13 m) and surface into the air pocket briefly, keeping regulators in. Continue south along the 30–40 m sandy gutter to 21 m and the secondary cave, then return north over the sand and a second ridge.

Beneath the Bay includes the Bubble Cave in its regular Black Rock dives; the Marine Life Network calls it a popular site close to the boat ramp. Sydney clubs and private boats also dive it.