Twin Peaks is a pair of rock spires rising from deep water on the Forestier Peninsula's exposed east coast. Go Dive Tasmania describes the site as twin pinnacles with large schools of fish and a swim-through at 35 m, diveable anywhere from 5 m on the tops to 40 m at the base. The Marine Life Network guide records the same area as the Sundial Caves, with the Twin Peaks spires, a maze of caves and boulder formations in 15-35 m, and walls covered in sponges, hydroids, gorgonian fans and anemones.

The dive combines the two great themes of this coastline: dramatic topography and the deep-water invertebrate gardens that the Eaglehawk Dive Centre calls its sponge gardens. On the upper spires kelp and brown algae dominate and fur seals sometimes flit past; below 20 m the rock becomes a patchwork of colourful sponges, sea whips and gorgonians, with butterfly perch in constant swirling schools. The caves and gaps between the boulders let divers weave through the structure rather than simply descending a wall, and the deep swim-through is a memorable feature for suitably qualified divers.

Banded morwong, boarfish, real bastard trumpeter and rock lobster are common. The site is best suited to Advanced divers with good gas management; those with Deep certification can use the full profile. Like the Sisters it is exposed and only reached on calm westerly days, and currents can be strong around the spires.

When conditions line up it offers a varied, three-dimensional dive that complements the wall at the Sisters and the caves of Waterfall Bay.

Boat access only. Eaglehawk Dive Centre's catamaran and Go Dive Tasmania's boat leave from the Pirates Bay jetty/boat ramp at Eaglehawk Neck (Old Jetty Road, off the Arthur Highway about 75 km and 1 hour 15 minutes from Hobart). The Forestier Peninsula sites lie north-east of Pirates Bay: the run across the bay and around Cape Surville takes roughly 15-25 minutes depending on sea state.

Private boats also launch at Pirates Bay; there are no public moorings on the offshore pinnacles, so boats drift-dive or anchor in sand well clear of sponge gardens and run a live-boat pick-up.

The Forestier Peninsula coast faces east and north-east into the Tasman Sea with no shelter from easterly weather. These sites need westerly or north-westerly winds and small swell (generally under about 1.5 m) from the east and south-east; north-easterly sea breezes that build through summer afternoons often shut them by midday, so trips run in the morning. Southerly groundswell wraps around Cape Surville and creates heavy surge on the shallow tops.

Currents are unpredictable and can run strongly around the points and pinnacles, especially on spring tides and when the East Australian Current pushes south in late summer. Autumn (March-May) gives the most frequent calm windows and the clearest water; operators decide on the morning of the dive.

Descend on one spire to the swim-through at about 35 m, pass through only if current and gas allow, then cross to the second peak and spiral up it through the sponge and gorgonian zone. Explore the cave maze at 15-20 m on the way up and finish with a safety stop on the top of a peak.

The 35 m swim-through is at the edge of recreational limits on air; nitrox for the shallower cave section; Deep Specialty required by operators for the deeper profile.

Go Dive Tasmania – lists Twin Peaks (5-40 m, Advanced or Deep) on its Tasman/Forestier boat days; Eaglehawk Dive Centre – part of its deep sponge-garden and canyon rotation in calm weather.