Weebubbie is the grandest of the Nullarbor's show-caves for divers. The CDAA describes a large talus-filled main passage heading south-west from the doline to two lakes; the large lake is about 150 m long, and a 100 m sump connects to further airspace and submerged passages, with a 150 m south-east offshoot. The smaller lake reaches 28 m. Visiting writers describe it as the biggest tunnel they have ever seen, with sun-baked orange-brown walls and vast bouldery terrain beyond the reach of torches, and water so clear it makes a swimming pool look murky.

Exploration dates to the 1970s: in late 1974 and August 1975 divers pushed the Railway Tunnel to about 40 m depth and 400 m length, facing decompression problems in depths over 33 m and noting long unexplored tunnels. More recent work has explored deeper sections, including the 'Snot Room' below 40 m, named for bacterial growths.

The CDAA tri-rates the site: the northern pool is Sinkhole-rated, the majority of the cave Cave-rated, and the deep section below 40 m, the Y-shaped tunnel and the Railway Tunnel are Advanced Cave-rated. Access requires written permission at least four weeks ahead (currently via proposals@dplh.wa.gov.au), a site indemnity for each visit, current CDAA cards and landowner permission.

Weebubbie is extraordinarily remote and physically demanding: equipment must be hauled down a 30-40 m drop and carried across boulders. It suits well-organised teams of cave-qualified divers prepared for a self-contained expedition. The same palaeontological richness that makes Nullarbor caves important – fossils of extinct megafauna have been recovered from the region's caves – means divers must avoid disturbing sediments and bones.

The Nullarbor caves lie along the Eyre Highway between Norseman and the SA border, roughly 11-14 hours' drive from Perth. Cocklebiddy Roadhouse (fuel, meals, water, showers) is the base for the central caves; Norseman, 435 km west, is the nearest regional centre. Access to the cave entrances is by unsealed station/bush tracks (4WD recommended), and all cylinders, compressors, gas, water and rope/hauling gear must be carried in.

Weebubbie is near Eucla, close to the WA-SA border, reached by 4WD track from the Eyre Highway. The entry requires a hauling frame for a 30-40 m vertical rope descent into the doline, then a long scramble down a talus slope into the main passage to the 150 m main lake. Written permission is required (see permit field).

Surface weather matters mainly for access and safety: summer temperatures can exceed 45°C, making gear hauls dangerous, while winter nights are cold. Heavy rain is rare but can flood entrances and destabilise rockpiles (the 1988 Pannikin Plains collapse followed a severe storm). Underwater conditions are stable year-round: groundwater at about 19°C (24°C at Tommy Grahams), often brackish to saline with haloclines, and visibility commonly 20-50 m or more unless disturbed.

Autumn to spring (April-October) is the usual expedition season. The main lake is still and clear; deep sections below 40 m require decompression planning.

Sinkhole-rated divers are limited to the northern pool. Cave-rated divers dive the main lake and first sump on laid line, managing depth to about 30 m. Advanced Cave divers can continue into the Y-shaped tunnel, the Railway Tunnel and the deep 'Snot Room' below 40 m with appropriate gas and decompression plans.

CDAA tri-rated: Sinkhole (northern pool), Cave (most of site), Advanced Cave (below 40 m, Y tunnel, Railway Tunnel). Apply at least four weeks in advance to proposals@dplh.wa.gov.au with indemnities, attendee list, dates, emergency contacts, CDAA cards and landowner permission. Trimix and staged decompression for deep sections; hauling frame and SRT gear for entry.

No operator – CDAA-rated divers by permission only.