Robb Jetty was built in 1921 to land livestock for the abattoirs at Robb's Jetty and served the meat works until it was demolished in the 1990s. What remains is a line of broken pylons and debris running about 120 m out from the beach below the CY O'Connor statue, the bronze of the engineer on horseback that stands in the shallows where he died in 1902. Nothing shows at the surface, so this is a navigation dive as much as a jetty dive.

The pylon stumps sit in about 4–8 m, with most of the dive around 5.5 m. They are well colonised by sponges, feather stars, ascidians and small corals, and scattered bottles, planks and metal give octopus and small fish shelter. Seagrass meadows along the southern side form a natural boundary and are worth a look for pipefish, cuttlefish and southern eagle rays. The bottom is silty sand but coarser than Ammo Jetty's, so visibility tends to be a little better, averaging around 6 m and reaching 10 m on good days.

Fish life is better than the flat approach suggests: cardinalfish, western talma, brown-spotted wrasse, crested and dusky morwong, striped trumpeter, yellowtail and silver trevally, wavy grubfish, boxfish, rough bullseye, batfish, flutemouth and lionfish. Gloomy octopus and giant cuttlefish are common, juvenile Port Jackson sharks turn up in winter, and blue-ringed octopus live in some of the bottles.

Robb Jetty suits divers comfortable with compass work and a surface swim who want something quieter than Ammo Jetty, and it is a good macro and night site.

From Fremantle take Cockburn Road south and turn west into McTaggart Cove, parking at the dog-beach car park at its end (busy at weekends; CCTV). Toilets and showers are near the car park entrance. Either cross the dunes from the north-west corner of the park and swim out on a bearing of about 300° for five minutes, or walk about 150 m along the beach to the CY O'Connor statue, find the concrete posts marking the old jetty's start and swim on about 245° for up to 120 m before descending.

The pylons cannot be seen from the surface, so take a bearing before you go. About 15 minutes from Fremantle.

The site faces west on an open beach inside Owen Anchorage, partly sheltered by Garden Island and the banks offshore. Dive in swell under about 1.5 m with light easterly winds. The afternoon south-westerly sea breeze in summer brings chop and cloudy water, so morning dives are best.

Strong westerlies and north-westerlies ahead of winter fronts wreck visibility and make the exit hard. Spring plankton and river outflow reduce visibility; the sandy bottom is coarser than Ammo Jetty's, so visibility often averages better, around 6 m.

Surface swim on your bearing from the statue or dune entry, then descend on the line of broken pylons at about 4–5 m. Follow the pylons offshore to their end at about 8 m, explore the debris and the seagrass edge to the south, then turn and follow the pylon line back towards shore. Surface on a bearing back to the beach, keeping watch for boats before ascending.

Used by metro dive schools for guided shore dives and as an alternative to Ammo Jetty; Bucket List Diver lists it for experienced Open Water or newly Advanced divers. Mostly dived independently.