Tabbagai Gap is the deepest of the reef sites along the Kurnell cliffs south of Cape Solander, and one of the least known. It lies off the southern part of Kamay Botany Bay National Park, where a gap in the cliffs (spelt Tabbigai or Tabbagai on different maps) is known to rock fishermen and walkers on the coastal track. Underwater the reef is formed by walls running roughly north–south and dropping from about 24 m to 28 m.

To the east the bottom is sandy with a few small boulders, although McFadyen notes this is an intermediate sand zone rather than the true sand edge, so the reef may extend further. The walls are cut by many small overhangs that shelter cuttlefish, Port Jackson sharks (particularly in winter) and even firefish, while schools of ladder-finned pomfret hang under the ledges and silver sweep and black reef leatherjackets move over the top. McFadyen's single dive here was made in huge seas with very poor visibility, yet he still found the site impressive and considered it worth several more dives in better conditions, so for now it remains largely unexplored.

It is a natural companion to nearby Tabbagai Point, the Desalination Plant Inlet and the Cape Solander sites, all within a few hundred metres. Because of the depth and the lack of shore reference, it suits experienced Advanced or deep-certified divers on private boats who enjoy discovering sites for themselves and are comfortable with limited information.

Boat only – the Kurnell cliffs are sheer and in Kamay Botany Bay National Park, with no practical shore entry. From Botany Bay, launch at Kyeemagh (Cooks River), Foreshore Road or Bonna Point (Silver Beach, Kurnell), run out past Captain Cook's Landing Place, Inscription Point and The Leap, then turn south along the cliffs; from Port Hacking (Gunnamatta Bay/Tonkin Park or Lilli Pilli ramps) run out past Bass and Flinders Point and north-east along Bate Bay past Cronulla Beach and Cape Baily. From Botany Bay head south past Cape Solander (about 20 minutes); from Port Hacking north past Cronulla Beach and Cape Baily (15–20 minutes).

McFadyen's GPS is 34° 01.4885' S 151° 13.9522' E. Run in on the northern end of Tabbagai Gap until the depth comes up from 28–29 m to 24–25 m and anchor there.

Exposed open-coast site between Cape Solander and Cape Baily, taking swell from the north-east through to the south-east and some wrap from the south. McFadyen's only dive here was in huge seas with very poor visibility, which shows how quickly it deteriorates; plan for seas under 1.5 m and several calm days beforehand. It is far enough from the bay entrance that tide matters less than at The Leap, but a big ebb after rain can still colour the water.

Morning dives avoid the summer north-easterly.

Anchor on the 24–25 m reef top, follow the north–south wall down to 28 m in one direction, looking in the small overhangs, then return along the base or top of the wall. The sandy bottom with small boulders to the east is not the true sand edge. Watch no-decompression limits; nitrox helps.

No regular charter – private boat or dive-club (St George Scuba Club) only