The West passage is the serious half of Engelbrecht Cave. Where the East passage is a short, shallow Cave-rated dive, the West runs roughly 300-340 m from the doline, reaching a maximum depth of about 12 m, and is graded Advanced Cave by the CDAA. The first sump is about 100 m long and leads to a major air chamber that lies directly beneath the Jubilee Highway – divers surfacing there are under one of the city's main roads. Beyond it a second sump ends in a small air chamber at a termination pool with space for only two or three divers.

The passage has narrow restrictions that demand single-file travel, and its biggest variable is water quality. Storm water from the city drains into the system, and after heavy rain the first sump can go from clear to zero visibility. On a good day the limestone walls are pale and the water clear; on a bad day it is a tactile, line-in-hand exit. This is why the West is restricted to Advanced Cave divers.

The history is the same as the East: named after distiller Carl Engelbrecht, explored by canoe in 1864, used as a dump, sealed in 1940, reopened and heritage-listed, and now a public attraction with dry tours and viewing platforms at both lakes. The combination of urban setting, long sumps and air chambers under the highway makes it a unique dive in Australia. It suits Advanced Cave divers with strong restriction and zero-visibility skills who want something different from the open sinkholes.

Engelbrecht Cave is on Chute Street in central Mount Gambier, a few minutes from the Jubilee Highway. Collect one of the two site keys from the Lady Nelson Visitor Centre, 35 Jubilee Highway East, during business hours, then park at the Chute Street site. Sign in at the site and tell the café/tour staff you are diving, unlock the gate and lock it behind you.

Carry gear down the steps and accessway (built for the dry tours) through the doline to the water; viewing platforms sit at the lakes in both passages. Diving is permitted 8 am-8 pm daily; return the key afterwards (after-hours return is possible).

Weather has no effect underground, but heavy rain matters: storm water drains into the doline and can contaminate the first sump, turning visibility from clear to zero, and water levels fluctuate seasonally, which changes airspace and restrictions. Avoid diving for several days after big winter storms. The site is a public tourist attraction with dry cave tours, so weekday mornings are quieter.

Water is a constant ~15°C.

From the west lake, follow the permanent line into the first sump (about 100 m), passing restrictions single-file, to the major air chamber beneath Jubilee Highway West; continue through the second sump to the small termination pool where 2-3 divers can surface. Check first-sump visibility before committing and turn on thirds or at the first sign of contamination.

CDAA grade: Advanced Cave (5L19/20), owner Mount Gambier City Council. Diving 8 am-8 pm; sign in/out; gates locked. Continuous guideline; thirds or stricter; three lights; low-profile or sidemount configuration advisable through restrictions; termination air chamber fits 2-3 divers only.

No commercial operator – CDAA Advanced Cave members only, using the Lady Nelson key system.