Stinging Nettle Cave is a ForestrySA Advanced Cave site near Tantanoola. The CDAA's description is brief but telling: low-profile dive configuration (sidemounts) is required, the entrance is slippery and needs care, and the cave is deceptively large once the restriction is negotiated at about 10 m.

That restriction defines the dive. Backmounted doubles will not pass, so divers configure sidemount, and the passage demands careful body position and line control. Beyond it the cave opens into a much larger space than the entrance suggests – a common pattern in the Gambier limestone, where narrow solution features connect to wider phreatic passages. No published survey, depth or visibility figures were found, so teams should seek a briefing from divers who know the site.

The name almost certainly comes from the nettles that grow around the entrance, a small hazard in itself for anyone kitting up in shorts. Being on forestry land, it is booked through ForestrySA's portal and closed on Total Fire Ban days. It suits experienced Advanced Cave sidemount divers who are comfortable with restrictions and want a quieter site than Tank Cave. Plan gas conservatively: the restriction slows exits and a silt-out on the way back through it is the scenario to rehearse. Teams usually dive it as pairs rather than larger groups, keeping the passage clear for one diver at a time. Treat it as a site to build towards after gaining restriction experience elsewhere. Its location near Tantanoola makes it convenient to pair with Fossil Cave or Tank Cave on the same trip, though the booking systems differ (ForestrySA versus DEW and CDAA).

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. The site is in forest near Tantanoola, about 25 km north-west of Mount Gambier.

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. The entrance is slippery, especially after rain.

Enter carefully, configure sidemount, negotiate the restriction at about 10 m on the line, then explore the larger cave beyond within thirds and exit through the restriction.

CDAA grade: Advanced Cave (5L186), owner ForestrySA. Sidemount/low-profile configuration required. Continuous guideline, thirds (or tighter because of restriction), three lights.

No operator – CDAA Advanced Cave sidemount divers via ForestrySA booking.