Nettlebed Cave was discovered and named by Adelaide cave diver Grant Pearce on 27 January 1990, and it is one of the more sensitive sites on the ForestrySA list. The CDAA lists it under its Cave heading, while the detailed page describes Advanced Cave-level demands – excellent buoyancy control and near-perfect finning technique.

The layout is a sequence of distinct rooms. A restrictive, mud-choked entrance leads to The Gallery, a chamber with markings of archaeological interest; beyond it is a larger chamber with boulders and silt, then a low, clay-floored passage into a final chamber at about 28 m. Actual penetration from the surface is about 80 m. The low passages and clay floors mean silt is ever-present, and the rules are to stick close to the permanent guidelines and avoid touching the ceiling, floor and walls.

Nettlebed is registered as a suspected Aboriginal site, and divers must comply with the Aboriginal Heritage Act 1988 – the markings in The Gallery are the reason for the care demanded, and any disturbance is both a heritage and a diving offence. Combined with the entrance restriction, this makes it a site for experienced, meticulous cave divers rather than a casual tick. It is booked through ForestrySA and closed on Total Fire Ban days. For those with the skills it offers a fascinating mix of cave diving and cultural heritage. Its discovery in 1990 also illustrates how much of the Gambier karst remained unknown until relatively recently, and exploration of new passage continues in the region. Visit only in small teams, and plan a slow, deliberate exit so that the fragile Gallery is passed once in each direction without contact.

Book online through the ForestrySA caving portal (forestrysa.com.au/caving – select the cave and date, then enter diver details); ForestrySA recreation staff can help by email (recreation@forestrysa.com.au) or on 08 8391 8800 during office hours. Collect the key as instructed (Mount Gambier Visitor Information Centre for most forestry sites), then drive into the Green Triangle pine plantations on forestry tracks using the booking directions. Park at the site, keep tracks clear for fire vehicles, and carry gear to the entrance.

Forestry sites are closed on declared Total Fire Ban days.

Underground sites are unaffected by swell or wind; the constraints are the ForestrySA booking, the key, and fire danger – all forestry sites close on Total Fire Ban days (frequent December-March) and fires are prohibited 1 November-30 April. Heavy rain turns forest tracks slippery and can wash debris into entrances. Water is a constant ~15°C, so long cave dives need drysuits.

Snakes are active near entrances in warm weather.

Pass the restrictive entrance carefully, follow the permanent guideline through The Gallery (do not touch the walls), into the larger boulder and silt chamber, then through the low clay-floored passage to the final chamber at about 28 m, roughly 80 m from the surface. Turn on thirds and exit on the line.

CDAA grade: listed under Cave on the CDAA directory; site page describes Advanced Cave requirements (5L290), owner ForestrySA. Stay on permanent guidelines; no contact with any surface; comply with Aboriginal Heritage Act 1988. Thirds, three lights, low-profile configuration.

No operator – CDAA members at the required grade via ForestrySA booking.