Meet the site
Lake St Clair, the southern end of the Overland Track and Australia's deepest lake, is the exception to the usual rule that Tasmanian lakes are too tannin-stained to dive. The Marine Life Network guide rates Cynthia Bay 4.5 out of 10 as a welcome change from ocean dives and an alternative when the sea is too rough: light penetrates to about 10 m, below which the water becomes dark and lifeless, so the best diving is in the 5 m shallows among small weed growths.
The guide describes freshwater crayfish (lobster-like, 10-15 cm, with large but harmless pincers), small shrimps and minute underwater spiders, with trout staying out of sight and fishing lures snagged in submerged branches. It notes that animals must not be removed (this is a national park) and that the water is much colder than the ocean, especially with spring snowmelt.
Around the lake there is world-class bushwalking, a visitor centre, cafe and accommodation at Cynthia Bay. It suits divers looking for something different, and snorkellers in summer, and it can be combined with a day walk to Shadow Lake or along the lakeshore towards Echo Point. The nearest hyperbaric chamber is the Royal Hobart Hospital, two hours away, and diving at altitude (737 m) requires altitude-adjusted decompression planning.
The lake lies within the Tasmanian Wilderness World Heritage Area, and visitors should follow Parks and Wildlife Service guidance, including checking and cleaning gear to avoid spreading freshwater pests and diseases such as chytrid fungus and didymo between waterways. Rangers at the Cynthia Bay visitor centre can advise on any current restrictions on in-water activities.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Lake St Clair (Cynthia Bay) is recorded as Freshwater Lake/River in Tasmania Freshwater & Caves. The listed access is shore. Confirm the actual meeting point, route and permission to visit; a map pin does not establish any of these.
Topics flagged by the stored research
These are questions prompted by the existing notes, not a verified or complete hazard assessment.
- Lines and obstructions
- Discuss any known entanglement concerns and the suitability of the planned area.
Historical access notes exist for this record, but have not been independently verified for current use. Request current directions from the operator or site manager rather than following an old entry description.
Questions, answered
Is Lake St Clair (Cynthia Bay) suitable for my certification?
The record lists Open Water. That does not establish suitability for every route or day. Share your training, recent experience and equipment needs with the operator and ask about the specific proposed dive.
Can I book Lake St Clair (Cynthia Bay) through YouDive?
YouDive is an independent research directory. Contact an operator directly to confirm whether it currently runs the trip, the inclusions and the booking terms.
What you might see
Freshwater crayfish, small shrimps, aquatic spiders, brown trout, small weed growths
Location
Shallow freshwater diving at Cynthia Bay, Lake St Clair - Australia's deepest lake - in Cradle Mountain-Lake St Clair National Park, with unusually clear water for a Tasmanian lake.
Facilities nearby
Cynthia Bay: visitor centre, cafe, toilets, accommodation and campground. Derwent Bridge: hotel and fuel. No air fills.
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
marinelife.org.auRecord updated 26 Sept 2026. Source claims are being reviewed.