Rapid Bay Jetty

Rapid Bay Jetty Dive Guide, Fleurieu Peninsula

By ScubaDownUnder Team · 2026-03-25

The old jetty is closed to divers. Since 23 June 2025 the water beneath the Old Rapid Bay Jetty, and within 20 metres of it on either side along its full length, T-head included, has been a prohibited area closed to all people and vessels. The Department for Infrastructure and Transport (DIT) has marked it with buoys and signs. Dive from the new jetty and stay outside the buoys: the old jetty's pylons and T-section, the dive Rapid Bay was famous for, can no longer be dived.

Rapid Bay is a small bay on the Gulf St Vincent side of the Fleurieu Peninsula, about 100 kilometres south of Adelaide, and for years it was where South Australian divers took visitors to find a leafy seadragon. Two things changed that in 2025. An inspection after a storm on 26 May found further safety risks at the old jetty, and the exclusion zone that had covered only its collapsing sections was extended to the whole structure. Over the same months the state's harmful algal bloom killed thousands of seadragons along this coast. This guide covers what you can still dive here, and what is and is not known about the seadragons since.

Two Jetties, One You Can Dive

BHP built the old jetty, the town and a limestone quarry between 1938 and 1942. The limestone went by sea to BHP's steelworks at Whyalla, Newcastle and Port Kembla, where it was used as flux. The jetty was 490 metres long with a 200 metre T-section for loading ships, ending in 9.1 metres of water at the lowest tide. Commercial use stopped in 1991, storms damaged it in 2004, and it was closed in stages after that; DIT says there has been no pedestrian access since late 2004.

For decades its pylons, crusted with sponges and soft corals and circled by schools of old wives and zebrafish, made it one of the best known dive sites in South Australia, and Diving Adelaide described the leafy seadragons as living underneath it. All of that habitat is now inside the prohibited area, so treat it as history.

The public jetty was completed in 2009, 50 metres east of the old one, to replace the access lost as the old jetty closed. It is 240 metres long, with a concrete deck, lights after dark and a staircase at the seaward end for divers and snorkellers. Diving Adelaide describes the entry as a platform and easy stairs towards the end of the jetty, with a giant stride possible at high tide. DIT's 2025 maintenance program replaced corroded steelwork and installed new access ladders, and DIT reports the works were completed that year.

No source we found gives a depth for the new jetty. The often quoted "under 10 metres" figure from Diving Adelaide and PADI describes the jetties as they were dived before the closure, and the new jetty is less than half the old one's length, so read your own gauge rather than relying on a published number.

What you can dive now is the water around the new jetty and the seagrass. The Scuba Divers Federation of South Australia (SDFSA) says divers can still dive the seagrass beds outside the exclusion zone, and describes the site as two jetties and extensive seagrass beds. Set your expectations accordingly: before the closure, Diving Adelaide said there was not much life under the new jetty and that it did not recommend diving it, partly because of the number of people fishing from it.

The Exclusion Zone

The rule is Notice to Mariners No. 41 of 2025, made under the Harbors and Navigation Act 1993. It covers the area beneath the old jetty and within 20 metres either side, from the yellow gate at its shore end along its entire length, T-head berth included, down to the seabed, and only people and vessels with the Minister's approval may enter. The District Council of Yankalilla's June 2025 update, passing on DIT's advice, put it simply: diving, swimming and boating are prohibited around the entire structure. According to the SDFSA's summary of the Act, entering without approval is an offence carrying a fine of up to $10,000, and a dive buddy, dive leader, instructor or boat operator who helps someone in can also be guilty.

The zone has grown in steps. After the old jetty was found partly collapsed on 10 January 2022, DIT barred boats, divers and swimmers from beneath it and within 15 metres either side. By 2024 the exclusion zone covered the collapsing wooden sections, and divers reached the T-section along an underwater trail of more than 40 star droppers, about 215 metres long, which SA Police Water Operations installed from the end of the new jetty in August 2024 at the SDFSA's request. That trail ends at the T-piece, so its far end now lies inside the prohibited area: do not follow it out. DIT carried out an engineering inspection of the old jetty in May 2025 and says it is still assessing the findings to decide next steps.

Because the new jetty sits only about 50 metres from the old one, the buoyed boundary is close to where you enter. Brief your buddy on where the buoys are before you get in, and stay on the new jetty side of them. In late 2025 the SDFSA reported that surveillance at the site had picked up divers still going under the old jetty, and warned that the structure could collapse without warning. With AusOcean it has petitioned the state to make the waters around the old jetty safe by removing the unsafe structures while keeping habitat for seadragons, and it is pressing a business case to reopen the area. Until DIT says otherwise, the old jetty is off limits.

Seadragons After the Algal Bloom

The leafy seadragon (*Phycodurus eques*) is South Australia's marine emblem, and Rapid Bay was the main site for Adelaide dive shops' leafy seadragon tours. Divers with Dragon Search SA identified, named and monitored dozens of individual seadragons at Rapid Bay and other sites in the years before the bloom. Weedy seadragons (*Phyllopteryx taeniolatus*) were seen too, but less often.

The 2025 bloom changed that. In September 2025 the IUCN's seahorse, pipefish and seadragon specialist group reported that thousands of leafy and weedy seadragons had died in South Australia, the largest recorded mass mortality of either species, and noted that Rapid Bay jetty, one of the main monitoring sites, was closed. In March 2026 the chief executive of Divers for Climate told InDaily that the site used to have about 45 known resident leafies and that local divers were now lucky to find one or two. The same report said a Divers for Climate supporter had seen 30 weedy seadragons on one dive at Rapid Bay a few weeks earlier, although instructor Carl Charter said weedy numbers had since started to drop off.

The SDFSA's own update, written in March 2026, is a little more hopeful: Second Valley and Rapid Bay seem to have been somewhat sheltered from the bloom, with strong numbers of weedy seadragons, the occasional leafy, blue devils, juveniles of many species and healthy seagrass and seaweed. No source we found says exactly where in the bay the seadragons are now, or how many live outside the exclusion zone. A 2019 account from the Marine Life Society of South Australia describes a small leafy in the seagrass bed near the jetty steps, so the seagrass is worth searching slowly, but treat any sighting as a bonus rather than a promise.

Seadragons are protected in South Australia. The SDFSA has asked divers not to disturb the seagrass beds and not to follow or touch seadragons, because it stresses them, and photographer Talia Greis, writing for Divernet, advises backing away if a dragon starts to rise. Diving Adelaide gives October to February as the leafy seadragon mating season, when males may be seen carrying eggs on their tails.

The 2025 to 2026 Algal Bloom

The bloom was identified in mid-March 2025 in waters around the Fleurieu Peninsula, near Waitpinga and Parsons Beach, and was caused by *Karenia* algae. As it spread it killed hundreds of thousands of fish, invertebrates and other animals on reefs, jetties and wrecks on both sides of Gulf St Vincent, and most of the sponges, soft corals, sea squirts and anemones on affected jetty pylons and reefs died. Testing has recorded zero or low levels of *Karenia* along the vast majority of the state's coastline since February 2026, and by March 2026 the SDFSA reported that Fleurieu waters had improved, with divers and snorkellers back in the water.

Before you go, check the latest testing results on the state government's algal bloom website and stay out of water that looks foamy or abnormally coloured. The SDFSA also recommends the SA Dive Sites Viz and Conditions Facebook group, where divers post current conditions and recovery sightings.

Marine Park and Fishing Rules

Rapid Bay lies in the Encounter Marine Park. The bay around the jetties is a general managed use zone (GMUZ-4), overlaid by a special purpose area for harbour works (SPA-1, "Harbor of Rapid Bay"), which runs from 138° 10.445' E to 138° 11.787' E and north to 35° 30.654' S. In a general managed use zone all recreational activities, including fishing, are allowed. To the west and north-west is the Rapid Head Sanctuary Zone (SZ-5), which the park's management plan summary describes as home to the leafy seadragon, with important headlands, boulder beach and seagrass habitats. Fishing is banned in sanctuary zones, but diving is welcome. Habitat protection zone covers the water to the north-east and east. The Ex-HMAS Hobart wreck lies inside the Rapid Head Sanctuary Zone.

Under PIRSA's rules, spearfishing is not allowed within 100 metres of a jetty, and nobody may carry or use a spear gun while diving on scuba or hookah. The SDFSA notes that the old jetty is still listed as an official jetty, so the 100 metre rule applies around it too.

Site Access and Logistics

Rapid Bay is about 100 kilometres, or roughly 90 minutes by car, south of Adelaide. The stairs are at the seaward end of the 240 metre new jetty, so expect to carry your gear the length of it. There are no toilets at the jetty; use the toilets at the Rapid Bay camping ground, which you pass on the right before the jetty car park, and where the SDFSA reports a defibrillator on the toilet block. There is no kiosk, so bring food and drinks. Diving Adelaide says the bay is protected from most winds except northerlies, and PADI's site page gives water temperatures of 17 to 20 °C and visibility of 5 to 15 metres.

Sea Dragon Dive Lodge, at 110 Finniss Vale Drive, Second Valley, about ten minutes' drive away, offers air fills, tank and gear hire, guided dives and accommodation. Diving Adelaide runs guided leafy seadragon tours to Rapid Bay, Second Valley or the Bluff at Victor Harbor, choosing the site on the day from conditions and recent sightings, while Adelaide Scuba says it will not run seadragon tours until the old jetty site reopens. Some operator pages still describe swimming from the new jetty across to the old one: that route is now inside the prohibited area, so confirm the dive plan with your guide.

If conditions or the closure rule out Rapid Bay, Second Valley is just up the coast and The Bluff at Victor Harbor is the other seadragon site Adelaide shops use. For questions about the exclusion zone, contact DIT on 1300 794 880 or DIT.Engagement@sa.gov.au.

Sources

- Department for Infrastructure and Transport (SA): Rapid Bay project page, dit.sa.gov.au/infrastructure/projects/rapid-bay - Department for Infrastructure and Transport (SA): Damage to Old Rapid Bay Jetty, 25 January 2022, dit.sa.gov.au - Department for Infrastructure and Transport (SA): New Rapid Bay Jetty works notice, September 2025, dit.sa.gov.au - Marine Safety SA: Notice to Mariners No 41 of 2025 (Temporary), 23 June 2025, marinesafety.sa.gov.au - District Council of Yankalilla: Community Update, Rapid Bay Jetties, 24 June 2025, yankalilla.sa.gov.au - Scuba Divers Federation of SA: Supporting SA's Jetties (Rapid Bay exclusion zone), sdfsa.net - Scuba Divers Federation of SA: Algal Bloom in South Australia, sdfsa.net - Scuba Divers Federation of SA: newsletters of August/September 2024, June 2025, September/October 2025, November 2025 and February 2026, sdfsa.net - InDaily: State emblem seadragon disappears from diving hotspot - IUCN SSC Seahorse, Pipefish and Seadragon Specialist Group: Thousands of seadragons dead in South Australia's worst recorded harmful algal bloom - Marine Life Society of SA: Concerns About the Welfare of Leafy Seadragons at Rapid Bay - Government of South Australia: Algal Bloom Update, algalbloom.sa.gov.au - Marine Parks SA: Encounter Marine Park - Department for Environment and Water: Encounter Marine Park Management Plan 2012 - Department for Environment and Water: Encounter Marine Park management plan summary - Marine Parks SA: Zones - Marine Parks SA: Diving - PIRSA: Hand fish spear, spear gun and powerheads, pir.sa.gov.au - Wikipedia: Rapid Bay, South Australia - Diving Adelaide: Dive the Rapid Bay Jetty - Diving Adelaide: Guided Leafy Sea Dragon Dives - PADI: Rapid Bay Jetty - Adelaide Scuba: Private Leafy Seadragon Scuba Tour booking page, adelaidescuba.rezdy.com - Sea Dragon Dive Lodge: home page, seadragondivelodge.com.au - Divernet: South Australia's Rapid Bay

Header photo: The old BHP jetty (left) and the new public jetty (right) at Rapid Bay, seen from the shore end of the new jetty in January 2014, by Peter Southwood, CC BY-SA 4.0, via Wikimedia Commons.