Stingray Bay – also called Breakwater Bay and, for its shape, The Horseshoe – is the small bay between Pickering Point and the Warrnambool breakwater where the Merri River meets the sea, and it is the heart of the Merri Marine Sanctuary. The sanctuary, 29 hectares of no-take water declared in 2002, runs from Thunder Point to Breakwater Rock, and Stingray Bay is its sheltered centre and the best shore dive and snorkel in Warrnambool. From the beach a sandy bottom slopes into a kelp forest that stretches from one side of the bay to the other, with fringing reefs on both flanks that hold swim-throughs, ledges and small caves. On the sand are the stingrays and flathead that give the bay its name; in the kelp and on the reef the Scuba Doctor lists sea sweep, big-belly seahorses, draughtboard sharks, southern eagle rays, calm crayfish sitting out at the front of their ledges, and giant Australian cuttlefish in the caves and weed, and Parks Victoria adds an abundance of the fish and invertebrates typical of this cool-water coast. Bottlenose dolphins and Australian fur seals come into the bay, and little penguins from the Middle Island colony hunt in the sanctuary waters.

Depths of 4–12 m, a sand entry from steps below the car park and a horseshoe shape that keeps navigation simple make this a genuine beginner's dive when conditions allow, and a long, slow one – 50 minutes or more is normal. The sanctuary status shows in the size and tameness of the crayfish and the number of fish. The constraint is the weather: the bay faces south-west, and although it is more sheltered than the points either side it requires very low swell, low tide and offshore winds, and becomes treacherous in any onshore wind. From here the channel between Middle Island and Merri Island, the sanctuary's deepest and richest feature, is a short swim to the west and is recorded separately. Middle Island itself is closed to the public to protect the penguin colony.

From the centre of Warrnambool follow Pertobe Road and Viaduct Road toward the breakwater; park on the western side of Viaduct Road near the first set of steps closest to the concrete wall, at the southern end of the parking area. The steps drop directly to the Stingray Bay beach, a walk of under a minute. Gear up at the car, carry down the steps and enter from the sand.

Exit the same way. Warrnambool Diving on Fairy Street, 2 km away, supplies air and guided dives; Daktari Surf & Dive hires snorkel gear.

The Merri Marine Sanctuary sites face south-west into the Southern Ocean and are, in the Scuba Doctor's words, prone to surge and swell, with conditions able to change quickly into dangerously rough seas with big swells and strong currents. Dive at low tide with a low swell (under about 1 m at Stingray Bay, under 0.5 m for the exposed sites) and light offshore northerly to north-easterly winds; any onshore southerly through westerly wind makes the sites treacherous. Check the water from the car park – if you see lots of white water, head home.

Visibility is best after settled northerly weather in autumn and poor after rain from the Merri River. Warm-water upwelling is absent; the Bonney Upwelling can bring cold green water in summer. Stingray Bay is the most sheltered of the sanctuary sites and is workable on more days than Pickering or Thunder Point, but the Scuba Doctor still requires very low swell and low tide.

Enter from the beach, swim out over the sand and descend on the edge of the kelp in 4–5 m. Work across the bay through the kelp forest from left to right, checking the fringing reef on each side for swim-throughs, crayfish under the ledges and cuttlefish in the caves, and the sand patches for stingrays and flathead. Turn at half gas, return through the kelp to the beach; toward the western side the channel to Middle Island begins and can be added in calm conditions.

Warrnambool Diving (Fairy Street) – air fills, PADI courses, divemaster-led local shore dives on request; Daktari Surf & Dive (Warrnambool) – snorkel gear and guided snorkels; Warrnambool dive club members dive the sanctuary regularly on calm days.