Second Valley is one of the prettiest spots on the Fleurieu coast, a small cove framed by folded cliffs and a short jetty, and it is a long-standing shore dive for Adelaide divers. The Federation describes the classic dive as a walk around to the second bay on the southern side of the jetty, where three small caves, including a swim-through with a right angle in it, are cut into the cliff face. The Marine Life Network adds small caves near the old boat winches south of the jetty and two caves at the base of the cliff at the southern point of the second bay.

Wikivoyage describes the headland as a fairly steeply sloping rocky reef of heavily folded sedimentary rock, probably shale or mudstone originally, dipping at about 25 degrees and running north-south, with a reef slope 15-40 m wide down to a sand bottom at about 9 m. Mixed kelp and other seaweeds grow at moderate density, and the rock shows through often enough to make the geology part of the dive. Fish life is often sparse, as the Federation candidly notes, but the site is known for occasional leafy and weedy seadragons in the weed and for small life in the caves and crevices: blue devils, wrasse, magpie perch, nudibranchs and crabs.

It is a relaxing place to explore rather than a fish-soup dive. Second Valley suits Open Water divers comfortable with a walk and a rock entry, and snorkellers exploring the caves on a calm day. It combines naturally with Lasseter's Reef and the jetty, and is a short drive from Rapid Bay.

Avoid it in any northerly or westerly swell.

Second Valley is about 1 hour 20 minutes (92 km) south of Adelaide via Main South Road; turn right at the Second Valley sign and follow the road down to the beach. Park at the end of the access road (limited spaces; busy on summer weekends); there are public toilets and a changing room but no drinking water. From the car park walk south past the jetty and the old boat sheds and winches around the rocks to the second of three small bays; enter there.

Alternatively enter from the rocky headland with the iron post at its tip, using the sheltered cove on the south side of the headland as an alternative entry and exit. The walk is a few hundred metres over rock.

Second Valley faces north-west into the gulf. It is sheltered from southerly and south-easterly weather and best in easterlies, but it is very exposed to northerly through westerly winds and swell and is not diveable in a big swell. Summer and autumn mornings, before the south-westerly sea breeze, are most reliable.

Tidal currents are small inside the bay but can be felt off the headland. Visibility is often good in calm weather and drops after westerlies and rain.

Enter at the second bay and follow the cliff south at 3-6 m to the two caves at the base of the southern point, then continue around the headland along the reef slope to 8-9 m. Return the same way, checking the weed for seadragons, and exit where you entered.

Underwater Sports (Edwardstown) – regular club shore dives; Diving Adelaide and other Adelaide shops – occasional guided dives; popular with independent divers and snorkellers.