Mud Hole is a small ForestrySA cave whose name is a fair warning. The CDAA description: the water is constantly shaded and consequently usually very clear; a flooded passage leads into a low silty chamber which pinches off 17 m below the surface; the site is very easily silted out by the first diver in.

So the dive has two states. For the first diver on a still day, shaded water gives surprisingly good clarity down the passage into the chamber, where the ceiling lowers and the floor is deep silt. For anyone following – or for the first diver on the way out – visibility can drop to nothing in seconds. That makes Mud Hole a small, short dive and an excellent, honest test of trim, frog-kicking and line following by touch.

The cave is Cave-rated and on forestry land, so it is booked through the ForestrySA portal and closed on Total Fire Ban days. There is little to see in terms of formations or life; the appeal is the challenge and the solitude. Many divers use it as a skills dive or as a second site after a larger cave. It suits Cave-rated divers with confident line skills who do not mind a short dive and a very muddy exit. Because it is short and close to Mount Gambier, Mud Hole is easy to fit in on a day already built around another forestry booking, and it is quiet – you are unlikely to share it. Treat each visit as a rehearsal for a real zero-visibility exit, with touch contact and line signals practised on the way out.

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.

First diver in leads with the line; follow the flooded passage into the low chamber, reach the pinch at 17 m, and exit promptly before your own silt overtakes you. Teams of two maximum work best.

CDAA grade: Cave (5L97), owner ForestrySA. Continuous guideline mandatory; touch-contact drills recommended; thirds; three lights; small teams.

No operator – CDAA Cave members via ForestrySA booking.