Meet the site
Althorpe Island is the wild outpost of Yorke Peninsula diving. Rising steeply from the sea at the mouth of Spencer Gulf, with a lighthouse first lit in 1879, it is surrounded by walls, reefs and boulder slopes, and the SDFSA describes more than 50 great dive sites around the island, with walls over 20 m, reefs, wrecks and seal colonies to 40 m. The Marine Life Society notes that the south-side cliffs drop straight to a rocky bottom at about 25 m, with more seals and larger blue groper than Haystack Island. The water here is oceanic and often clear, and the marine life reflects the exposure. Walls and caves carry sponges, gorgonians and soft corals, and the fish life is prolific: big western blue groper, schools of sweep, bullseyes, boarfish, blue devils, snapper and trevally. Australian sea lions and New Zealand (long-nosed) fur seals haul out on the island and join divers in the water, especially at Seal Cove, where the Marine Life Society describes a population of over 150 playful seals. Crayfish and abalone are present in season. The island is also a shipwreck site. The Investigator Strait Shipwreck Trail lists the SS Pareora (1919) and Mylor Star (1982) as dive sites here, plus several vessels not yet located – Young St George (1878), Welling (1892), Rapid (1937) and Altair (1971). Althorpe is an advanced destination: remote, current-swept, weather-exposed and deep in places. It needs a capable boat, a careful forecast and experienced divers. For those who get there on a good day, it offers some of the best temperate diving in South Australia outside Kangaroo Island.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Althorpe Island is recorded as Island in Yorke Peninsula. The listed access is boat (day trip). 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.
- Current and timing
- Ask how the operator assesses the current window for the actual route. Historical tide notes are not a departure instruction.
- Planned depth
- Confirm the intended route and training requirements; the recorded maximum is not a target.
- Water movement
- Ask how swell and local exposure affect the proposed entry, exit and route.
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 Althorpe Island suitable for my certification?
The record lists Deep/Advanced + experience. 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 Althorpe Island 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
Western blue groper, Australian sea lions, New Zealand fur seals, sweep, bullseyes, boarfish, southern blue devils, snapper, trevally, southern rock lobster, abalone, sponges, gorgonians, soft corals
Location
Steep-sided granite and limestone island with a lighthouse about 8 km south-west of Cape Spencer at the entrance to Spencer Gulf, with 20 m+ walls, reefs, seal colonies and several wrecks; more than 50 dive sites to 40 m.
Facilities nearby
None; Marion Bay ramp and services.
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
sdfsa.netthediveshack.com.aumarinelife.org.auenvironment.sa.gov.auRecord updated 27 Sept 2026. Source claims are being reviewed.