The Monarch was a three-masted wooden schooner built in 1871 (at Moreton Bay, Queensland, according to earlier records), one of the many small sailing vessels that serviced the ports of Spencer Gulf. On 1 April 1909 she failed to tack off the southern shore of Wardang Island; the Department for Environment and Water records that her anchor would not hold against the tide, and she was driven ashore and wrecked. The remains lie in about 2 m, making the Monarch a snorkel rather than a scuba dive.

What survives is a scatter of timbers, iron fastenings and fittings among weed and sand along the shore, much of it periodically buried and exposed as sand moves. The site is interesting mainly for its place in the trail's story: together with the Australian and MacIntyre, it shows how dangerous the island's southern shore was for vessels waiting to load or sheltering from weather. Small reef fish – sweep, magpie perch, leatherjackets and juvenile fish – shelter around the timbers, and crabs and octopus use the gaps.

It suits snorkellers and divers looking for a short surface interval activity between the deeper Wardang wrecks. As a fragile timber site, it should be viewed without touching, and nothing should be moved or removed. Because the site is so shallow and close to shore, sand movement after winter storms can reveal more of the hull structure one year and bury it the next, so two visits rarely look the same.

Photographers get the best light on calm, sunny middle-of-the-day visits, when the timbers and weed stand out clearly against the pale sand.

From Adelaide drive about 190 km (2 hours 15 minutes) via Port Wakefield and Maitland to Port Victoria. Launch at the Port Victoria boat ramp beside the jetty and run west to Wardang Island – the island's nearest shore is about 8 km away and the southern wreck sites about 11 km (20-30 minutes in a small boat). The Port Victoria Maritime Museum and the Department for Environment and Water trail booklet give site details and coordinates.

Wardang Island is Aboriginal land held by the Point Pearce (Narungga) community: diving the wrecks from a boat is fine, but landing on the island requires permission. The Monarch lies on the southern shore of the island, about 10 km from the ramp (20-25 minutes), between the Investigator and the Australian. Anchor in sand off the site and snorkel in; it is too shallow to bring a boat close.

Wardang Island lies 8-11 km off Port Victoria in Spencer Gulf. Its western and southern shores – Aagot, Investigator, Notre Dame d'Arvor, Monarch, Australian and MacIntyre – face the open gulf and are subject to south-westerly swell, surge and wind-driven sand movement, so they need low swell and light winds, ideally easterlies. The eastern and northern sites (Songvaar, Moorara) are more sheltered from the prevailing south-westerlies but exposed to northerly and easterly chop.

The 20-30 minute boat run from Port Victoria becomes uncomfortable above about 15 knots. Summer and autumn mornings are the usual window; winter fronts bring days of south-westerly weather. At 2 m the Monarch is essentially in the surge zone and needs flat conditions.

Snorkel over the site at low swell, following the scattered timbers and fittings along the shore, then return to the boat. Scuba adds little at this depth.

No regular operator; occasionally snorkelled on Wardang trail trips.