Sandra's is a plate-coral bommie in Dillon Bay, about 400 m offshore from Little Boat Harbour at Bremer Bay. Marine Life Network describes it rising from 18 m on the sand to 8 m at its top, with blue groper, swallowtails and old wives among a variety of fish, rich sponge and invertebrate life, and a large area of gorgonian fans on its south-eastern side. Small boats can launch at Little Boat Harbour, making it a quick trip.

The plate coral here is the main draw – broad, layered sheets of Turbinaria-type coral that seem out of place in 18°C water, supported by the warm Leeuwin Current's influence that extends along the south coast. Bremer Bay Dive's guided scooter dives to a plate-coral site highlight the same feature, along with the chance of weedy and leafy seadragons over the surrounding weed.

The bommie is compact enough to cover in a single dive, with the deeper gorgonian field on the south-east side and the coral-covered top giving a natural multi-level profile. Blue groper are large and inquisitive, and schools of swallowtails and old wives circle the top.

It suits Open Water divers comfortable with boat entries, and makes a good complement to the shore dive trail at Little Boat Harbour. Private boat owners should use the published GPS mark and anchor on sand to avoid damaging the coral. There are no moorings or facilities at the site, and Bremer Bay is a long way from medical help, so carry oxygen, a first-aid kit and a VHF radio, and log your trip with the Bremer Bay sea rescue group or someone ashore.

Bremer Bay is about 180 km (2 hours) north-east of Albany and 500 km (5-6 hours) south-east of Perth via the Albany Highway and Borden-Bremer Bay Road, or via the South Coast Highway and Bremer Bay Road. Air fills, hire gear and guided dives are available from Bremer Bay Dive in town. Sandra's lies about 400 m offshore in Dillon Bay at S 34° 28.051', E 119° 21.370'.

Small boats can be launched at Little Boat Harbour; larger boats use the Bremer Bay boat harbour and run around to Dillon Bay (a few minutes). Anchor in sand beside the bommie.

Dillon Bay is sheltered from the prevailing south-westerly swell but exposed to easterly and south-easterly winds and swell. Dive it in westerly weather or calm summer mornings before the south-easterly sea breeze fills in, usually by late morning. Swell over about 1.5 m from the south-east makes anchoring uncomfortable.

Visibility is better offshore at the bommie than at the beach sites, typically 10-18 m, and falls after storms.

Descend the anchor line to the base of the bommie at 16-18 m, circle it to the south-east side to see the gorgonian fans, then spiral up to the plate-coral top at 8-10 m for the rest of the dive and the safety stop.

No regular scheduled trips; Bremer Bay Dive's scooter dives visit a plate-coral site in the area; otherwise private boats.