Two small wrecks off the Bicton shore are among the most reliable places in the Swan River to find seahorses. The ALC40 was an Australian Army landing craft of the Second World War, operated by the 43rd Landing Craft Company. She broke her mooring in a storm in 1943 and sank where she lies, in 8.5 m about 70 m from shore. The steel hull measures 18.5 m by 5.5 m but rises only a foot or two above the riverbed, so it is easy to swim over without noticing. It is, however, covered in life.

A few metres east lies the Gay Dragon, a privately owned wooden pleasure craft built to look like a Chinese junk, which sank on its mooring in the 1980s or early 1990s. Very little remains apart from upright ribs, the engine block and a fuel tank, spread over about 8 m by 2 m. Divingwawrecks says the site is almost guaranteed for seahorses and regarded as the most popular place to find them in the river.

Besides seahorses, the wrecks hold nudibranchs, anemones, gobies, blennies, bream, porcupinefish and crabs, and they are good at night.

The wrecks lie in a river bottleneck with slight currents almost always present, and visibility can drop to under a metre with the tide. They suit Open Water divers with compass skills and patience.

River temperatures swing more than the ocean: about 22–26 °C in late summer but as low as 13–15 °C in winter, when a 7 mm suit or drysuit makes a long dive more comfortable. Rinse gear well afterwards, as the estuary water is often high in organic matter.

Drive to the Sea Scouts hall on Jerrat Drive, Bicton, near Bicton Baths, about 10 minutes from Fremantle. Park nearby, kit up and enter via the collapsed boat ramp beside the scouts' mast. The ALC40 lies about 70 m from shore at S 32°01.647' E 115°46.258', and the Gay Dragon is a few tens of metres east at S 32°01.653' E 115°46.284'.

Tow a flag on the swim.

Sheltered from ocean swell. The wrecks lie in a bottleneck of the river opposite Point Roe, so slight currents are almost always present; neap tides and slack water are best. Visibility varies from about 6 m to less than 1 m depending on the tide and rainfall.

Boat traffic is heaviest on warm weekend afternoons, so early mornings and evenings are calmer.

Swim or descend from the collapsed ramp on a compass bearing to the ALC40 at 8.5 m, circle it slowly searching for seahorses, then move east to the Gay Dragon's ribs, engine block and fuel tank. Return to the ramp on the reciprocal bearing.

Dived independently and on club and shop night dives, often together with Bicton Baths.