Five Fathom Bank is a long ridge of limestone reef running roughly north–south about 3 nautical miles west of Garden Island. It forms the outer edge of the protected waters off Rockingham, and it has caught many ships, including the Orizaba (1905) and the Sepia (1898). For divers it is an area rather than a single site: kilometres of reef, bommies and gutters in 5–20 m, often with the reef top just below the surface.

The City of Rockingham describes abundant and diverse fish life on the bank, with dolphins, crayfish, tuna and sharks, and it is also a well-known fishing ground. The Marine Life Network describes Seaward Reef, an outcrop of the bank, as scattered limestone reefs and bommies, very exposed and affected by inshore currents, with a calmer inner side and better visibility.

Because it sits in open water beyond the shelter of Garden Island, visibility is usually better than inshore, often 10–20 m. The reef carries kelp and sponges, with ledges and overhangs where buffalo bream, bullseyes, dhufish, queen snapper, blue groper, western rock lobster and wobbegongs shelter.

The bank is exposed and needs calm days, a GPS and a sounder, and a boat crew who can recognise breaking water. It suits experienced boat divers who want to explore beyond the charted wrecks. Published site-level detail is limited, so treat this as a general record of the bank. Divers who explore it often combine a reef dive with the Orizaba at the bank's southern end, and use the sounder to pick out ledges before descending.

Launch at Point Peron, Woodman Point or the Rockingham ramps and run west past Garden Island or round Cape Peron to the bank, about 3 nautical miles off Garden Island. A GPS and sounder are essential, as the reef tops often lie just below the surface. There is no fixed mooring; anchor in sand patches.

Allow 15–25 minutes each way depending on the ramp and the section of bank.

Very exposed to the open ocean; dive only in calm conditions with swell under 1 m. Seaward Reef is affected by inshore currents, and its inner (eastern) side is calmer with better visibility. The summer sea breeze builds from late morning; winter westerlies and north-westerlies close it for long periods.

Anchor in sand beside a reef section identified on the sounder, descend to 10–15 m and follow the reef edge, exploring ledges and bommies before returning to the anchor. On Seaward Reef, dive the calmer inner side.

No regular operator. Visited by private boats and clubs, often combined with the Orizaba.