Engelbrecht Cave is the cave dive under a city: the doline sits in the middle of Mount Gambier on Chute Street, and its two flooded passages run east and west beneath houses and the Jubilee Highway. The site is named after Carl Engelbrecht, a German settler who in 1885 turned a nearby flour mill into a whisky distillery and used the cave for waste disposal. It was explored by canoe in 1864, bought by council in 1929, sealed in 1940, investigated by divers in 1964, cleaned up by the Lions Club in 1979, heritage-listed in 1995 and, since 2024, opened for guided dry tours with a café, viewing platforms and toilets.

The East passage is the Cave-rated half. From the lake it runs roughly 70 m, with a maximum depth of about 8 m, along a low, flat, silty passage that leads to an inner air chamber with its own lake, plus side passages and two further sumps of roughly 10-20 m each. It is shallow, intimate and relatively short, and the challenge is not depth or distance but silt: the floor lifts at the slightest disturbance, and the ceiling is close enough that trim and frog kicks are essential. Divers enjoy surfacing in the inner air chamber – an eerie, still room far from daylight beneath the town.

For newly rated CDAA Cave divers it is one of the most useful sites in the region: close to accommodation and fills, simple key access, fixed hours of 8 am-8 pm, and a passage that rewards good technique. Beyond the East passage lies the Advanced Cave-rated East Extension, which has its own row and rules, and the West passage is covered separately.

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.

Kit up at the east lake platform, tie in a primary reel to the permanent line, and follow the low, flat, silty passage about 70 m to the inner air chamber and its lake, exploring side passages only within grade. Two short sumps of 10-20 m continue beyond. Turn on thirds and exit slowly to avoid lifting silt behind you.

CDAA grade: Cave (5L19/20), owner City of Mount Gambier/City of Grant. Diving 8 am-8 pm; sign in/out; gates locked. Continuous guideline from open water; rule of thirds; three lights; low-profile configuration helps.

Cave divers must not pass beyond the main chamber rockpile into the Advanced Cave East Extension.

No commercial dive tours – CDAA Cave-rated members self-organise with the Lady Nelson key; dry cave tours run by the City of Mount Gambier's contractor.