Split Bommie is a deep-water site on Opal Reef that Scuba IQ describes as wide open spaces, a hotspot for macro photography with nudibranchs and tiny crustaceans. It is listed among Opal's named sites by I Love Cairns as well. As its name suggests, the bommie is divided, with a cleft running through it, creating extra surfaces and crevices.

The appeal is the small stuff. The surfaces of the bommie are covered in sponges, hydroids and encrusting corals that provide habitat for nudibranchs, flatworms, shrimps, crabs and other small invertebrates. Patient divers who slow down and look closely will be rewarded with a variety of colourful critters, making this a favourite with macro photographers.

The surrounding area is open and deep, giving the site a feeling of space. Larger animals such as reef sharks, rays and schooling fish may pass through, but the focus is usually on the bommie itself. Scuba IQ does not publish depths; the description as a deep-water site suggests the base lies beyond 20 m.

Divers should plan carefully, as time spent searching for macro subjects can quickly use up no-decompression time. Current can run around the bommie, so it is best suited to divers with some experience. Visibility is typically 15–30 m.

Split Bommie suits experienced divers and macro enthusiasts who want a change from the coral gardens and walls. Bring a macro lens or a magnifier and take your time – this is a site that rewards patience. It is used mainly by small-group operators, so ask for it by name if macro is your interest.

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 bommie and work slowly over its surfaces at 15–20 m hunting for nudibranchs and crustaceans, keeping an eye on depth and NDL. Ascend gradually around the bommie and finish on its top or the reef edge for the safety stop.

Calypso Reef Cruises – daily Opal trips (3 dives/snorkel sites); Wavelength Reef Cruises – snorkel-only daily trips to exclusive Opal moorings; Scuba IQ / Blue Dive and Tech Dive Academy – small-group dive days several times a week; private charters.