Long Bommie is a satellite reef rising from about 25 m beside the main body of Opal Reef. Wavelength, which visits it for snorkelling, notes that it is being monitored for the recovery of its plate corals after cyclone damage, which makes it an interesting site for anyone curious about how the reef heals. Satellite reefs like this stand apart from the main reef, so they catch the tidal flow and attract fish.

The bommie's sides and top were once covered in large plate corals; cyclones can shatter such plates, leaving rubble, but fast-growing Acropora species can recolonise within a few years if conditions are favourable. Divers visiting today can see the recovery in progress – young plates and branching colonies re-establishing on the old reef structure – alongside surviving massive corals, soft corals and sea fans. The fish life benefits from the bommie's isolation.

Expect schools of fusiliers and anthias over the top, trevally and other predators hunting in the current, and reef sharks cruising around the base. Turtles are common on Opal and are frequently seen resting or feeding on bommies. The depth range – from near the surface to around 25 m – makes the site suitable for divers of all levels, with deeper sections for experienced divers and the top for snorkellers and beginners.

Current can run past the bommie, so divers should be prepared to stay in its lee if necessary. Visibility is typically 15–30 m. Long Bommie is a good site for divers interested in reef ecology and recovery, and it offers the classic bommie dive profile – start deep, spiral up – that makes navigation straightforward.

Ask the guides about the monitoring programme; Wavelength's marine biologists track changes at the site.

Boats to Opal Reef leave Crystalbrook Superyacht Marina on Wharf Street, Port Douglas; Calypso Reef Cruises checks in around 8:15 am for a 9:00 am departure and returns about 4:30 pm, and Wavelength and Scuba IQ/Blue Dive leave around 8:00 am. Park in the marina car park or on surrounding streets (free all-day parking along Wharf/Dixie streets), or use the operators' courtesy pick-ups from Port Douglas and the northern beaches. Opal is about 60 km north-east of Port Douglas; the crossing takes 80–90 minutes, part of it threading through the protected Tongue Reef maze.

Divers gear up on board and enter by giant stride at a mooring; on Calypso some sites are reached by tender from the main vessel. The skipper chooses three sites on the day depending on wind and tide.

Opal is a crescent-shaped outer reef near the continental shelf edge. Its shape gives some shelter from the south-east trades that blow from about April to September, so several moorings (Bashful, Sno, Blue Buoy) stay diveable in 15–20 knots, but a 25-knot-plus trade wind makes the crossing rough and operators may cancel. Exposed sites on the seaward face and in the channels between North, Middle and South Opal are dived only in light winds and suitable tides.

October–December is typically calmest with the best visibility; the wet season (December–April) brings northerlies, storms, cyclone risk and marine stingers (November–May). Tidal currents run through the gaps between the Opal reef sections and around bommies, strongest on spring tides – channel and bommie sites are timed for neaps or slack water.

Descend to the base of the bommie (up to 25 m), circle it at depth looking for the regrowing plate corals and pelagics, then spiral up the sides and finish on the top for the safety stop.

Wavelength Reef Cruises – snorkel visits; small-group dive operators (Scuba IQ / Blue Dive, Tech Dive Academy) and private charters for scuba.