Brush Island is a small, uninhabited island about 800 m off Murramarang Beach, just south of Bawley Point. It marks the northern end of the Batemans Marine Park and is best known to divers as the place where the SS Northern Firth was wrecked in 1932. The island is fringed by rocky reef. To the south-east and east a shallow reef runs out from the island; the ship hit a submerged part of it that was not on the chart. Around the outer side the reef drops to sand in the mid-20s, with boulder slopes, gutters and kelp typical of the South Coast.

There is little published site-by-site information. Divers who visit describe the usual temperate mix: kelp beds in the shallows, sponge and sea squirt growth on deeper rock, and schools of yellowtail, silver sweep and sweep over the reef. Eastern blue devilfish, blue groper, morwong and wobbegongs are common. NSW fisheries lists Brush Island as grey nurse shark critical habitat, so grey nurse sharks can gather in the gutters and special rules apply to divers and fishers. Whales pass close by in winter and spring.

Dive Adventures Ulladulla lists the island as an experienced-diver trip with depths beyond 25 m, and usually combines it with the Northern Firth wreck. The long run from either Ulladulla or Batemans Bay means few divers come here, so the reef is seldom disturbed. It suits divers with some boat-diving experience who want somewhere less visited.

Boat access only. From Ulladulla Harbour it is roughly 20 km south, about 45 minutes, past Bawley Point to the island off Murramarang Beach. From Batemans Bay (Hanging Rock ramp) it is a similar run north past Durras and Point Upright.

There is no public mooring; anchor on sand or rubble on the sheltered side appropriate to the day's swell. Small craft sometimes launch through the surf at Bawley Point or Kioloa, but only in very calm seas.

The island is exposed to swell from north-east through south-east and has shallow reef to its east that breaks in big seas. Pick the sheltered side for the day: the western (landward) side in easterly swell, the northern side in a southerly. The long boat run needs a stable forecast with swell under about 1.5 m and light winds, ideally a westerly morning before any sea breeze.

Southerly changes can arrive quickly. Visibility falls after heavy rain.

Anchor on the sheltered side and follow the reef edge around the island at 10–18 m, turning at half gas. Look into the gutters and boulder piles for wobbegongs and blue devilfish, and scan the sand edge. If you are combining it with the Northern Firth, dive the wreck first as it is deeper.

Dive Adventures Ulladulla runs occasional Brush Island trips (listed at max 25 m+, experience required), usually combined with the Northern Firth wreck. Otherwise private boats from Ulladulla or Batemans Bay.