Ewens Ponds is the gentle counterpart to Piccaninnie – three round, spring-fed sinkholes on Eight Mile Creek, each about 9-10 m deep, joined by shallow channels and so clear that visibility beyond 80 m has been reported. It is the one Mount Gambier freshwater site where Open Water divers can join a guided tour without any cave training, and it is one of the region's classic snorkels.

The appeal is the plants. Because the water is so clear, aquatic vegetation grows to about 6 m depth, and National Parks SA notes species that are not found growing fully submerged anywhere else in the world. The pond walls drop steeply from the edge, lined with swaying green growth, down to floors of fine white silt; in the channels the current eases you over meadows of weed a metre or two below the surface. The third pond contains a small natural cave, and the whole 365 m route is swum one-way, from Pond 1 to Pond 3, in about 30-45 minutes. Wildlife is modest but interesting – eels, small native fish, freshwater crayfish and crabs – and the underwater light on a bright day is superb for photography.

The rules exist to protect a fragile Ramsar-quality wetland: groups of 2-6 snorkellers, one one-hour slot per person per day, full-length wetsuit, short fins under 55 cm, no weight belts, no standing, no swimming back upstream. Scuba is allowed only on accredited guided tours, and freediving and inflatables are banned. In recent years falling groundwater and algae have forced closures and changed permit conditions, so availability is not guaranteed. When it is open, Ewens suits beginners, snorkellers, families with children over six and photographers who want an easy, beautiful freshwater dive.

From Mount Gambier drive south about 25 km towards Port MacDonnell, turn east onto Ewens Ponds Road and follow it to number 69 and the Conservation Park car park (sealed parking, bus parking, toilets). Gear up at the car, walk the short path to the First Pond entry platform. The route through the ponds is one-way: enter at Pond 1, drift and fin through the channels, and exit at Pond 3 (365 m in all), then walk back along the track.

Snorkellers need a DEW booking; scuba is only allowed as part of a guided, accredited tour.

No swell or tide; a gentle current flows through the channels from Pond 1 to Pond 3. Sunny middays give the best light on the plants. Heavy rain has little effect as the ponds are spring-fed, but occasional blue-green algae blooms and – recently – low groundwater have closed the site; operators noted it reopening after a low-water closure with modified permit conditions.

Wind makes the surface swim in the channels choppy but is rarely a problem. Check the National Parks SA booking page for the current season.

Enter at the Pond 1 platform, descend the steep sides to 8-10 m and circle the pond, then rise into the shallow channel and let the flow carry you over the weed to Pond 2; repeat, look into the small natural cave in Pond 3, and exit at the Pond 3 platform. Never swim backwards against the flow or stand on the vegetation.

CDAA lists the site as 'Not Rated' – open to Open Water divers, but scuba only on a guided accredited tour under current DEW conditions. No overhead except the small cave in Pond 3 – do not enter.

Scuba only with an accredited guided tour: Dive Experience (Mount Gambier) runs guided Ewens Ponds dives and an Ewens/Kilsby double (Wed and Sat, Open Water, max 10 m) when the ponds are open; Reef 2 Ridge (Mount Gambier) has run snorkel/scuba tours. Snorkellers may self-guide on a DEW booking.