Cod Rock sits on the south-eastern side of Split Solitary Island, on the opposite side of the island from the dramatic natural cleft — the 'split' — that gives the island its name, and is one of the more distinctive individual bommie dives in the group. The bommie itself is separated from the fringing plateau by a gutter around 18 m deep, rising up to a peak near 14 m before dropping away again to about 21 m on its outer face, giving the site real vertical relief for a relatively compact structure. The site's headline resident is a large black cod, reported at around two metres long, that has made this bommie its home and is generally reliably found lurking under one of the overhangs on the structure — a genuine big-fish encounter at a depth well within Open Water range, which is part of what makes Cod Rock a popular request among Jetty Dive Centre's regular customers.

Blue devil fish shelter under the same overhangs, adding a splash of striking colour to the site, and a second, smaller bommie nearby holds red morwong and other resident reef fish for those wanting to extend the dive beyond the main structure. Because the site is built around a single, fairly compact bommie rather than a long stretch of reef, Cod Rock rewards divers who take their time circling the structure at different depths rather than swimming past it quickly, and its slightly greater depth range compared with the shallower Split Solitary Island moorings puts it a notch up in recommended experience level. On a good visibility day, this is one of the most satisfying single-feature dives in the whole marine park.

Jetty Dive Centre departs from the public floating pontoon wharf in Coffs Harbour boat harbour, opposite the Attitude Burgers building (check in at 398 Harbour Drive). Private boats use the public ramp inside the harbour breakwall. Split Solitary Island is the closest of the group, about 9 km east-north-east of Coffs Harbour, roughly a 20-minute run — the standard backup site when weather rules out South Solitary Island.

Conditions off Coffs Harbour depend heavily on which island is being run: North West Solitary and Split Solitary sit closer inshore and are usable in more marginal weather, while South Solitary and any northern sites need a bigger settled window. Visibility across the group is generally 8-25 m and best away from river influence; the Coffs, Bellinger, Nambucca and Clarence systems all periodically dirty inshore water for a few days after heavy rain. Summer (Nov-Apr) is warmest with tropical vagrants and mantas; winter (May-Oct) is cooler with grey nurse sharks and giant cuttlefish.

Humpback whales pass April-November. Being the closest and most sheltered island, Split Solitary is the most reliably diveable site in the group, though visibility is often lower than at South Solitary Island since it sits closer to the mainland's influence.

Descend into the 18 m gutter separating the bommie from the plateau, circle the bommie itself from 14 to 21 m looking for the resident black cod under overhangs and blue devil fish, then visit the smaller nearby bommie for red morwong before ascending.

Jetty Dive Centre runs Split Solitary Island daily as either the main destination on rougher days or a second dive after South Solitary Island; also used extensively for training and check-out dives.