Tumby Bay's jetty is the Eyre Peninsula's best-known seadragon dive. The Marine Life Society describes an easy, shallow shore dive in 2-4 m with colourful pile growth, lots of crabs, nudibranchs, leafy seadragons, sea cucumbers, blue-throated ascidians, cowfish and magpie perch, over a seagrass bottom with 5-7 m visibility. Diving Adelaide rates it as its favourite jetty dive after Rapid Bay and Edithburgh.

The piles support growth similar to the old Rapid Bay jetty, and the seabed alternates between weedy patches and sand. That weed is the key: as Diving Adelaide puts it, the weeds under and around the jetty create the perfect habitat for seadragons' camouflage. Leafies are less frequently seen than at Rapid Bay or The Bluff, but when found they can be large – Diving Adelaide reports two near-maximum-size animals of about 45 cm on one visit.

Seahorses and nudibranchs are the other highlights. Fish numbers are limited and macro life is less abundant than at the Yorke jetties, because the bottom has fewer rocks. The dive is gentle and shallow, suitable for new divers and snorkellers, and local tour operators run guided seadragon snorkels.

Its distance from Adelaide limits its popularity, but it is a natural stop for divers travelling to Port Lincoln or visiting the Whyalla cuttlefish in winter. The Port Lincoln Times has profiled the 'lovely leafies of Tumby Bay' as a local attraction. Choose a day with westerly winds, when the water is flattest and clearest, and search slowly – the dragons are masters of disguise.

Tumby Bay is about 600 km (6.5 hours) from Adelaide via Port Augusta and the Lincoln Highway, or 50 km north of Port Lincoln (airport). The jetty is at the end of the main street on the foreshore beside the town centre. Park in the car park at the jetty base; the entry and exit stairs are close by, so the gear carry is short.

Swim out along the piles over the weed and sand. Diving Adelaide typically visits on its winter cuttlefish trips, 2.5 hours' drive from Whyalla.

The east coast of Eyre Peninsula faces Spencer Gulf, so easterly, north-easterly and south-easterly winds blow onshore, raise chop and stir the sand and seagrass, while westerly winds blow offshore and give the flattest, clearest water. There is little ocean swell this far inside the gulf, although strong south-easterlies can produce a short, steep sea. Tides are moderate, and shallow jetties are easiest around mid to high water.

Summer afternoons often bring south-easterly sea breezes, so mornings are best; winter has more westerly weather, which suits this coast, but colder water (about 13-14°C).

Enter by the stairs and fin slowly along the piles, then leave the jetty and zig-zag over the weed on either side scanning for leafy seadragons; check the piles for seahorses and nudibranchs on the way back.

Diving Adelaide includes it on winter Whyalla cuttlefish trips; Experiencing Marine Sanctuaries runs guided seadragon snorkels; otherwise independent divers and locals.