Muttonbird Gutter, on North Solitary Island, takes its name from the wedge-tailed shearwater — commonly called the muttonbird — colony that nests on the island above during the warmer months, a breeding population significant enough that parts of the island itself are closed to visitors during nesting season, much as Mutton Bird Island at Coffs Harbour is. Underwater, the gutter is a typical North Solitary Island feature: a channel through the broken reef in roughly 8 to 20 m, sitting within the same general area as Anemone Bay, Fish Soup and Elbow Cave. Marine life here follows the pattern of the rest of North Solitary Island's southern reef system: turtles move through regularly, wobbegong sharks and moray eels occupy the gutter walls, and the generally excellent visibility this far from the mainland — usually 15 to 25 m — makes for pleasant, unhurried exploration of the reef's crevices and overhangs.

The gutter does not carry a singular headline feature in the way Elbow Cave's anemone beds or the Boulders' scale do, but it is a solid, reliable component of a broader day's diving around this section of the island. The connection to the muttonbird colony above gives the site an interesting ecological link between the surface and underwater worlds rarely made explicit at other Solitary Islands sites, and divers with an interest in seabirds may find the association adds a layer of context to what is otherwise a straightforward, pleasant gutter dive. As with the rest of North Solitary Island, reaching it requires the full 75-minute commitment from Wooli and a genuinely settled weather window.

Wooli Dive Centre departs from the Wooli River wharf; the river mouth has a shallow, shifting bar that the operator's purpose-built jet-propulsion vessel is equipped to cross. Trips to North Solitary Island run about 75 minutes each way, weather dependent, with a minimum group size typically required.

North Solitary Island sits fully in the open ocean and trips depend on a genuinely settled weather window; the Wooli River bar can be dangerous in a big swell or strong outgoing tide. Visibility is normally excellent (15-30 m). Winter is cooler but often calmer; summer brings warmer water and more current.

Descend into the gutter at 8-12 m, work along its length to about 18-20 m looking for turtles and reef fish, and shallow up for an extended ascent given the typically good visibility.

Wooli Dive Centre includes Muttonbird Gutter on North Solitary Island trips as conditions and group interest allow.