Dungeons & Dragons is Bougainville Reef's cave dive. Mike Ball describes a maze of caves, tunnels and swim-throughs at the reef top, with a wall descending about 1,000 m beyond the shallows where sharks and barracuda patrol. Marinelife.org.au lists it among Bougainville's cave and cavern sites.

The maze is formed within the coral structure of the reef top, a series of chambers and tunnels linked by openings where light filters through. The caves are typically shallow, so divers can explore them at moderate depths and with ambient light at the entrances, though a torch is needed to see the life inside. Sponges, encrusting corals and soft corals line the walls, and squirrelfish, soldierfish, sweepers and cardinalfish shelter in the darker sections, with lobsters and shrimps in the cracks.

The contrast with what lies outside is part of the appeal. Emerging from the tunnels, divers find themselves on the lip of a sheer wall that plunges into the deep, and Mike Ball says sharks and barracuda are common there. Grey reef and whitetip sharks cruise the edge, and trevally and tuna make passes from the blue.

The caves are not true overhead environments requiring cave training, but they do involve swimming through enclosed spaces, so good buoyancy, awareness of fellow divers and care not to stir sediment are essential. Divers uncomfortable in enclosed spaces can stay on the reef top and wall. It suits intermediate divers and pairs well with Crystal Plateau and the Antonio Tarabocchia on a Bougainville day, giving three quite different dives on one small reef.

Liveaboard only. Mike Ball's Spoilsport visits Bougainville on its 4-night Osprey fly-dive (Cairns departure Thursday evening, return by flight from Lizard Island), 5-night Coral Sea & Cod Hole and 7-night Coral Sea expeditions; the overnight run from Cairns is roughly 230 km of open ocean. Bougainville is not guaranteed on every itinerary and is usually allocated one day.

Dungeons & Dragons is on Mike Ball's 4-night Osprey, 5-night and Far Northern itineraries and is dived from a mooring.

Bougainville is a small, isolated Coral Sea reef about 230 km north-east of Cairns and 150 km south of Osprey, with no land to shelter behind, so the surface can be choppy in any SE trade wind over about 20 knots, common June to August. Conditions broadly follow Osprey's, though Bougainville is sometimes calmer when Osprey is windy. Currents are generally mild but can pick up on the corners and walls.

September to December usually gives the calmest seas and best visibility (20–40 m); December to April is cyclone season.

Descend to the reef top at 8–12 m, follow the guide through the cave and tunnel maze using a torch, then exit onto the wall and descend briefly to 20–25 m to look for sharks and barracuda. Return to the reef top for the safety stop.

Mike Ball Dive Expeditions (Spoilsport) – 4-night Osprey fly-dive, 5-night Coral Sea & Cod Hole and 7-night Coral Sea expeditions from Cairns; Bougainville included on most Coral Sea departures when weather allows.