Blue Lagoon is a lesser-known coral-garden site on the southern Ribbon Reefs. It is named in the 'additional sites' list of Mike Ball's 7-night Coral Sea exploratory expedition and appears on its Cod Hole–Ribbon Reefs itinerary map among the southern moorings, alongside Steve's Bommie, Flare Point, Fish Market and Circle of Life.

That matches Mike Ball's descriptions of the neighbouring southern Ribbon gardens, Flare Point and Summer Bay, which have bright blue and yellow Acropora, big Porites boulders and resident cuttlefish, and it is likely Blue Lagoon shares the same character. The name suggests a sheltered pocket of the reef with clear blue water over a sand bottom.

If so, expect a shallow, bright, easy dive with long bottom times, well suited to photography and snorkelling. Typical fauna in these gardens includes blue-green chromis and damselfish over the branching corals, sweetlips and coral trout under plate corals, trumpetfish, parrotfish, surgeonfish, giant clams, whitetip reef sharks and lagoon rays on the sand, and turtles. In June and July dwarf minke whales range around Ribbon Reef No. 3, which is close by.

Published descriptions of the site itself are scarce, and this record should be treated as provisional until an operator description is available. It suits divers of every level and makes a relaxing alternative to the deeper pinnacles of the southern Ribbons, especially for a late-afternoon dive when the light is warm and the fish are active over the coral.

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 Blue Lagoon on some Coral Sea and Ribbon Reef itineraries.

Divers enter by giant stride from the dive deck at the mooring and descend the mooring line. It appears on Mike Ball's itinerary map in the southern group with Steve's Bommie, Flare Point and Fish Market and is dived from the mooring.

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.

Descend to about 10–12 m and follow the coral gardens, looking for cuttlefish among the Acropora, then drift up to the shallows at 3–5 m where the largest Porites boulders stand. Use the shallows for a long safety stop.

Mike Ball Dive Expeditions (Spoilsport) – occasional on 7-night Coral Sea and Ribbon Reef itineraries.