Rapid Bay is internationally recognised as one of the best places in the world to see a leafy seadragon, and the new public jetty is where every dive now begins. The concrete jetty, opened in 2009, runs about 240 m out over flat sand and seagrass and ends in a large steel staircase with a landing at about low-tide level. Beside it stands the old 1942 BHP ore-loading jetty, whose piles, T-section and famous 'Cathedral' made the site's reputation.

Until mid-2025 the classic dive was to cross from the new jetty to the old one and explore its heavily encrusted piles. Storm damage in May and June 2025 led the Department for Infrastructure and Transport to impose a 20 m exclusion zone around the old jetty for divers, swimmers and boats, and at the time of writing that zone remains in place pending a decision on the structure's future. Divers can still use the new jetty, the navigational trail installed in 2024, and the extensive seagrass beds outside the exclusion zone, which is where leafy seadragons often forage.

The new jetty's concrete piles are smoother and less colonised than the old timber and steel ones, but still host sponges, ascidians and algae, and the seagrass, gravel and rubble patches around them support a remarkable range of life. Leafy and weedy seadragons, giant cuttlefish, bobtail squid, blue-ringed octopus, anglerfish, nudibranchs, bull rays and eagle rays are all recorded, along with schools of trevally, yellowtail, old wives, snook, silver drummer, morwong, boarfish and bullseyes. Dolphins and sea lions visit occasionally.

The site is shallow (mostly under 10 m), sheltered in southerly weather and suits every level of diver, from snorkellers to underwater photographers who return again and again. Seadragons are protected: keep your distance, never touch or chase them, and back off if one rises vertically, a sign of stress. Natural light gives the truest colours.

Watch for anglers' lines and squid jags around the jetty.

Rapid Bay is about 1 hour 30 minutes (about 100 km) south of Adelaide via Main South Road; turn right at the Rapid Bay turn-off past Delamere and follow the road down to the bay. Park in the long, narrow unsealed car park as close as 60 m from the new jetty (a ground sheet helps when gearing up). Walk the new concrete jetty about 240 m to its outer end – a handcart or trolley is useful – where a large steel staircase with handrails descends to a landing at about low-tide level.

From the landing, divers explore the new jetty and seagrass and, since 2024, can follow a navigational trail toward the old jetty's T-section; a line of stakes on the sand guides divers across the gap. Note the 20 m exclusion zone around the old jetty (see Old Rapid Bay Jetty). Boats can come from Wirrina Cove (Marina St Vincent) or Cape Jervis.

Rapid Bay faces north, so it is sheltered from southerly and south-westerly weather but exposed to winds and swell from the north-west through north-east. January to April is the best period, when the prevailing pattern blows offshore (south-easterlies). Strong northerlies make the stairs rough and stir the bottom; visibility below about 5 m makes navigating between piles difficult.

Tidal currents are usually slight, although a westward drift has been noted on a rising tide with no wind, and the ranger service warns of strong tides at times; neap dodge tides are easiest. The site is diveable year-round when winds are southerly. The 2025 harmful algal bloom affected the area; check recent reports.

Descend from the staircase landing to the sand at about 5 m and explore the new jetty piles and seagrass edges for leafy seadragons. Follow the marked trail/stakes toward the old jetty only as far as the exclusion zone allows, search the seagrass beds outside the zone, then return to the staircase. Compasses can be affected by the steel – use the piles and stakes for navigation.

Altitude after diving: the route back to Adelaide crosses hills to about 225 m (and higher on some routes) – factor into ascent/surface interval planning.

Sea Dragon Dive Lodge (Second Valley) – guided leafy seadragon dives most days by arrangement; Diving Adelaide (Glandore) – regular guided two-dive trips from Adelaide; Adelaide Scuba, Underwater Sports and clubs – frequent trips. Dived daily by independent divers in good weather.