Clam Gardens, which Mike Ball calls the Clam Beds, lies between Ribbon Reefs No. 4 and 5, and its residents are the reason to go: a group of around 14 giant clams (Tridacna gigas) between 1.5 and 2 m long, some believed to be well over a century old. They sit in the shallows at 2–7 m among hard-coral gardens, fine white sand and boulder Porites, their mantles glowing blue, green and gold in the sunlight.

Dive the World describes four large coral bommies rising from a sandy base at about 15 m to within a few metres of the surface, with overhangs and small caves in the 5–6 m range and nurseries of staghorn coral. It rates the site highly for photography because the shallow depth gives bright light and long bottom times.

Around the clams, schools of bumphead parrotfish graze the coral, and diagonal-lined sweetlips, blue-green chromis, green and loggerhead turtles, whitetip reef sharks and Queensland groupers are common. Garden eels rise from the sand, and nudibranchs and parrotfish are everywhere. Mike Ball's photographers' guide recommends the lowest tides for split shots of clams with the reef flat behind them.

This is one of the easiest dives on the Ribbons, suitable for novice divers and snorkellers, and one of the best-value dives for photographers. It is a reminder of what giant clams were like before overharvesting removed them from much of the Indo-Pacific; the Great Barrier Reef is one of the few places where populations of this size survive.

Liveaboard only (or fly-dive via Lizard Island). Mike Ball Dive Expeditions' Spoilsport and Spirit of Freedom depart Cairns (Trinity Wharf / Marlin Marina) in the evening and steam north overnight, roughly 12–14 hours and 200–250 km, to reach the Ribbon Reefs by morning; some itineraries fly Cairns–Lizard Island (about one hour, scenic flight along the coast) and board or disembark there. Trips run 3–7 nights and include Clam Gardens on many Ribbon Reef itineraries.

Divers enter by giant stride from the dive deck at the mooring and descend the mooring line. The clams lie in 2–7 m of water close to the mooring, so the site is dived and snorkelled straight from the boat.

The Ribbon Reefs sit on the edge of the continental shelf and take the full south-east trade wind from April to October. Lagoon-side moorings stay diveable in 20–25 knot SE winds, but reef-front sites and passes need lighter winds; liveaboards shelter behind the reefs overnight. September to December is usually calmest.

Tidal flow through the gaps between the Ribbons is strong on springs, so exposed pinnacles are timed for slack water. December to April brings rain, lower visibility and cyclone risk; box jellyfish and Irukandji are possible November to May. A shallow, sheltered site best on calm days; the lowest tides are best for split-level photographs of the clams.

Descend to the sand at about 15 m beside the bommies, circle the four main bommies, look into the small caves at 5–6 m, then spend the second half of the dive in the 2–7 m shallows visiting the giant clams. Use the shallows as a long safety stop.

Mike Ball Dive Expeditions (Spoilsport) – Ribbon Reef and Coral Sea itineraries from Cairns, several departures a month; Spirit of Freedom – 3-, 4- and 7-night trips from Cairns/Lizard Island, weekly.