Piccaninnie Ponds is the best-known freshwater dive in Australia and one of the reasons Mount Gambier appears on cave-diving bucket lists. The park protects a spring-fed karst wetland listed under the Ramsar Convention, where groundwater from the Gambier limestone aquifer emerges so filtered that visibility has been described as some of the clearest anywhere. The system has three named features: the First Pond, an open depression about 10 m deep with a silty floor; the Chasm, a narrow sinkhole dropping beyond 100 m; and the Cathedral, an enclosed cavern about 35 m deep with sculpted white limestone walls.

The First Pond is the approach to everything else. You glide over meadows of bright green aquatic plants, stonewort and algae that sway in the gentle spring flow, with small native fish, eels and freshwater shrimp among the stems. The silt floor is fine and easily raised, which is why the permit system insisted on full-length wetsuits, no standing and careful finning. Snorkellers could float the length of the pond and look down into the Chasm's blue void; divers used it as a shallow warm-up before going deeper.

The ponds have a sombre history – several divers died here between 1969 and 1984, part of the run of fatalities that led to the formation of the Cave Divers Association of Australia and the site-grading system still used today. More recently the ponds have suffered from falling groundwater and a filamentous algae outbreak, and National Parks SA has closed the ponds to diving and snorkelling until further notice while the vegetation regenerates. When it reopens it will again suit careful snorkellers and CDAA-rated divers; for now it is a walk-and-look site with boardwalks and viewing points.

From Mount Gambier take regional roads south-east towards Wye and the SA–Victoria border (about 32 km), then turn onto Piccaninnie Ponds Road to the signed park entrance. Park in the sealed car park (bus parking available), walk the short boardwalk/track (a couple of hundred metres) to the ponds with gear; there is a divers' changing shelter and interpretive shelter. Mobile coverage is unreliable, so print your permit.

The park is free to enter, but water entry needs a DEW permit – and at the time of writing no permits are being issued.

Weather has little effect underwater – there is no swell, current or tide – but surface conditions matter for the long gear carry and surface intervals. After very heavy winter rain surface run-off can cloud the upper few metres. Summer brings the best light shafts around midday and algae growth in the shallows.

Private and forestry land may be closed on declared Total Fire Ban days (common December-March), so check the CFS fire-ban forecast the night before. Groundwater levels in the Lower South East have been falling, which has caused closures of the DEW ponds sites in recent seasons. Piccaninnie Ponds is presently closed for all immersive activities because of a filamentous algae outbreak and reduced groundwater inflow; check the National Parks SA alerts page before planning.

When open: enter from the platform, fin slowly across the First Pond over the weed beds at 3-8 m, keeping well off the silt floor, and follow the channel to the lip of the Chasm. Divers within grade drop over the Chasm lip (see separate row); snorkellers and those not continuing turn at the lip and return along the opposite side of the pond. Slots were one hour, so plan a 45-50 minute dive.

CDAA grade: Basic Cave (5L72) – scuba permits only for CDAA members rated at sinkhole/Basic Cave level; snorkel permits open to anyone. Historical permit conditions: min 2 / max 4 per group, max 8 people per one-hour slot, max two slots per person per day, divers book 10+ days ahead with DEW indemnity (valid one financial year, re-submit after upgrading grade). First Pond itself has no overhead.

Currently closed to diving and snorkelling. When open, snorkel permits were available to anyone and scuba permits only to CDAA members rated at sinkhole (Basic Cave) level; Diving Adelaide, Dive Experience and CDAA instructors ran trips. No operator can take divers while the closure stands.