Somerton Reef is one of the lesser-known inshore reefs of Holdfast Bay, listed in the Sea Wolves Dive Club's Adelaide metro site list and on Wikivoyage as a boat-access reef dive with a maximum depth of about 6 m. Geographically it belongs to the same system of low limestone reefs and ancient shoreline outcrops that run along the Adelaide coast between Glenelg and Seacliff. Those reefs typically form low ledges and scattered rock on a sand and seagrass seabed, with short algae, sponges and ascidians on the rock and fish such as old wives, magpie perch, leatherjackets, wrasse and blue devils sheltering under the edges.

Divers visiting Somerton should expect something similar, in shallow water with plenty of light. The site's advantages are its shallow depth and short boat run from Glenelg, which make it a potential second dive or training dive. Its disadvantage is that shallow inshore reefs off Adelaide are highly sensitive to weather: westerly winds and swell reduce visibility quickly.

Anyone planning to dive Somerton should obtain an up-to-date GPS mark from the Sea Wolves or Scuba Divers Federation of SA, dive it on a calm, clear day, and consider reporting what they find to the Federation or the Marine Life Society of SA, both of which maintain local site information. Photos and species records from such dives help fill gaps like this one.

Boat access. Launch at the Glenelg (Holdfast Shores) ramp or West Beach ramp and run south along the coast for about 5-10 minutes to the GPS mark off Somerton Park. Anchor in the sand beside the reef; there is no mooring.

Sources list the site only as a boat dive; although it is relatively close to shore, a shore approach would mean a long surface swim across a surf-affected beach and is not documented.

A shallow inshore site that is only worth diving after several days of offshore easterly winds and flat seas. Westerly and south-westerly winds or swell stir up the sand and make it unpleasant and murky, and the summer south-westerly sea breeze usually ends diving by early afternoon. Runoff after heavy rain from nearby stormwater outlets reduces visibility for days.

Tidal movement is small; mid to high tide adds a little depth over the reef.

Anchor beside the reef and swim a slow circuit at 4-6 m, keeping the reef on one shoulder and returning to the anchor by compass.

No regular operator – private boat and club dives only (listed by Sea Wolves Dive Club and Wikivoyage).