The Chimney lies a little south of The Tunnel at the southern end of Black Rock. McFadyen describes a large sand gutter that runs north-west into the reef from a sandy and rocky bottom at 21 m. Divers descend on the south-east ridge, swim south or west and drop over a sheer wall to reach the gutter. Along the gutter are overhangs decorated with gorgonians and yellow zoanthids, and at its head is a dark cave entrance. After 5–10 m the cave opens out into a hole – The Chimney – that exits through the top of the reef. The Marine Life Network describes a cave with a 4 m tunnel at the back that exits into open water and is full of fish.

Other features include a sand-filled hole 3–4 m across, several walls and corners, and a rock ridge that rises about 2 m off the sand and runs south-south-east. The reef behind the chimney is at about 12 m and the eastern wall reaches just over 18 m. Fish include eastern blue devilfish, bullseyes, blue groper and schools of yellowtail and sweep, with wobbegongs in the cave. The rock carries sponges, sea squirts, gorgonians and zoanthids.

The dive suits Advanced divers comfortable in a short overhead passage with light at the exit. It pairs naturally with The Tunnel and can be part of a longer drift along the south end of Black Rock. Bring a torch for the cave and for the colour under the overhangs, where the zoanthids glow yellow in torchlight.

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 the site is about three minutes from the ramp.

Anchor on the south-east ridge, away from the chimney opening.

Sheltered from southerly swell by the headland, but open to easterly and north-easterly swell, which surges through the cave and chimney. Pick days with swell under about 1.5 m from the east. Visibility falls after heavy rain and big seas stir up the sand gutter.

Descend on the south-east ridge, swim south or west and drop over the sheer wall to the sand at 21 m. Follow the big sand gutter north-west into the reef past overhangs to the dark cave entrance. Swim 5–10 m through the cave, come up through The Chimney to the reef at 12–15 m, then return via the eastern wall (18 m) to the anchor after about 20 minutes' exploring.

Beneath the Bay dives The Chimney and The Tunnel at Black Rock's southern end; Spirit Divers also listed it. Visited by Sydney clubs.