Marion Bay Jetty

Marion Bay Jetty Dive Site Guide | Yorke, SA

By ScubaDownUnder Team · 2026-04-21

Marion Bay sits at the entrance to the southern Yorke Peninsula just before the road enters Innes National Park, and its jetty occupies a transitional position between the sheltered upper gulf sites and the more exposed southern coast that the national park contains. The water is clearer here than the northern peninsula sites, a function of the deeper, more open conditions at this latitude, and the combination of sea dragons, cuttlefish, and the visibility that a calm day in this part of the gulf produces makes it a worthwhile stop on any southern Yorke Peninsula dive itinerary. For divers basing in Marion Bay for a multi-day trip into Innes NP, the jetty is the easy bookend dive at the start or end of a day on the more demanding southern coast sites.

The bay opens to the west and northwest, and the jetty extends into water that deepens to around 7–8 metres at the outer end. The seagrass beds are extensive, stretching away from the jetty structure on the sandy floor in both directions, and it is in these beds, particularly in the zone directly adjacent to the pylons where weed meets structure, that weedy sea dragons are most reliably found. Leafy sea dragons are sighted with less regularity but are present at the site, and the lower depth and better visibility than the northern sites make spotting them more achievable on a productive day. Both species are slow movers and tolerate close observation by neutrally buoyant divers; both are also extremely well camouflaged.

Giant cuttlefish aggregate here in the winter months with more predictability than at the smaller northern sites. The breeding behaviour of male cuttlefish, the intense colour changes, the competitive posturing, the deliberate slow approach to a female, is on display through the July-to-October window and is one of the most compelling wildlife encounters South Australian diving offers. Outside the breeding season, cuttlefish are present individually and in pairs throughout the year, hovering above the structure with the characteristic composure of an SA cephalopod that has not been harassed by human contact.

The encrusted pylon surfaces carry the standard SA jetty community, sponge, ascidian, encrusting bryozoan, with a turnover of nudibranch species across the seasons. A torch helps with the shaded faces of the pylons, where the sponge growth is densest and the smaller invertebrate species concentrate. Schools of yellowtail and silver trevally pass through the water column on tide changes, and the southern blue-ringed octopus is reliably present in the rubble zone, the standard SA jetty warning applies, no touching under any circumstances.

The fish life on the structure is the supporting cast, old wives, magpie morwong, leatherjackets, and the smaller temperate reef species working the encrusted faces. Wobbegong sharks rest on the deeper rubble pockets through the warmer months, and Port Jackson sharks aggregate in the cooler months when their breeding cycle brings them inshore. Pipefish in the seagrass beds adjacent to the pylons reward the patient diver willing to drop face-down into the canopy and search slowly through the weed.

The northwesterly wind exposure is the practical variable at Marion Bay. These are the prevailing winds for the southern Yorke Peninsula coast, and they arrive with enough energy to chop the surface and reduce visibility in the shallow seagrass zone within hours of picking up. Planning a morning dive before the sea breeze establishes is the consistent strategy for this site and the others in the Innes Park vicinity. Visibility on a calm morning typically runs 8–14 metres, with the better days reaching 16+ metres after a stretch of settled offshore weather.

Water temperature ranges from 13°C in winter to 20°C in February, with a 7mm wetsuit the sensible default, the southern Yorke Peninsula does not get the warm-water relief that the upper gulf produces, and the long bottom times the shallow site permits make the heavier suit worth the bulk. For divers based at the Marion Bay caravan park, the jetty is a five-minute drive and a manageable 90-minute round trip including kit and dive, the easy logistics make it natural to slot in around the more demanding [Ethel Wreck](https://www.scubadownunder.com/dive-sites/ethel-wreck) and West Cape sites that justify the longer multi-day trip.

## Site Access and Logistics

Marion Bay is approximately 265 kilometres from Adelaide via the Yorke Peninsula Highway and the Southern Yorke Peninsula road. The drive from Adelaide is around three and a half hours. The township sits just north of the Innes National Park boundary. Entry is from the jetty steps, straightforward giant-stride or seated entry. Open Water certification is appropriate for the depth.

The Marion Bay caravan park provides a practical base for multi-day diving combining this site with the Ethel Wreck, Stenhouse Bay, and [West Cape Reef](https://www.scubadownunder.com/dive-sites/west-cape-reef). Tank fills are available in Yorketown (approximately 45km north on the Yorke Peninsula Highway), plan a fills run for any multi-day trip into the southern peninsula. Innes National Park entry fees apply for the surrounding southern coast sites.

A 7mm wetsuit is the practical standard. Combine with morning diving to beat the northwesterly sea breeze; afternoon dives are routinely shut down by wind chop on the shallow seagrass zone. The site is suitable for newer divers in calm conditions and combines naturally with the more advanced sites in Innes NP for an itinerary that spans the difficulty range.

## Sources

- [Black Point Jetty](https://www.scubadownunder.com/blog/black-point-jetty-yorke-peninsula-dive-review) - [Cape Spencer Reef](https://www.scubadownunder.com/blog/diving-cape-spencer-reef-yorke-peninsula-sa) - [Klein Point Barge](https://www.scubadownunder.com/blog/klein-point-barge-dive-site-guide) - [Hardwicke Bay Jetty](https://www.scubadownunder.com/blog/hardwicke-bay-jetty-dive-site-guide) - Department for Environment and Water SA, Innes National Park - Atlas of Living Australia, Leafy and weedy sea dragon distribution