Split Solitary Island, only 9 km from Coffs Harbour and reachable in about 20 minutes, is by far the most heavily used site in the marine park precisely because its proximity and generally sheltered aspect make it diveable on days when wind or swell rules out the more exposed islands further offshore. The southern side, where most of the named moorings sit — Shrimp Mooring, Cowry Mooring, Moray Mooring, Lobster Lair, Mike's Mooring, The Wall and Kingfisher Point among them — follows an irregular drop-off marking the edge of a shallow plateau at around 10 m, with the bottom flattening out and gradually deepening to 15-18 m beyond it. The names of the individual moorings are a fair guide to what divers find at each: moray eels, egg cowries and banded coral shrimp are resident throughout the area, and the flat sections beyond the drop-off are thickly covered with hard and soft corals, sponges, ascidians, bryozoans, tube worms and algae, providing exceptional habitat for nudibranchs and other small invertebrates.

Turtles move through regularly, and the general resident reef-fish population is dense even by Solitary Islands standards, making this less a single dramatic dive site than a rich, continuously interesting stretch of reef that rewards slow, attentive diving. Because Split Solitary is the default fallback for Jetty Dive Centre whenever conditions elsewhere are marginal, it also carries the bulk of the operator's training and check-out dives, and visibility here is typically lower than at the more exposed South Solitary Island, since the site sits closer to the mainland's river and creek outflows. What it lacks in the singular spectacle of Manta Arch, it makes up for in reliability and sheer density of smaller, photogenic marine life, and for many visiting divers this becomes the site they end up doing most often simply because it is the one most likely to actually run.

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 at whichever named mooring is assigned, follow the irregular drop-off from the 10 m plateau edge down to 15-18 m checking crevices for moray eels and shrimp, and finish on the shallower plateau top for the ascent.

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.