Top Slip Point is on the western shore of North Bruny Island, facing Tinderbox across the northern D'Entrecasteaux Channel, north of Trumpeter Bay. The Marine Life Network guide describes soft sedimentary cliffs that have eroded to leave rubble on the bottom and create small caves, cracks and swim-throughs in about 5 m. It calls it a pretty, shallow dive for naturalists and photographers: the shaded caves are coated in zoanthids, jewel anemones and sponges – the same deep-water community that grows in the caves of the Tasman Peninsula, here in just a few metres.

Fish include bullseyes in the dark recesses, weedfish, bearded rock cod and trumpeter. The guide advises staying in the shallows, since the bottom at around 15 m is flat and featureless. The site's shallow depth means long dives and plenty of light at the cave mouths, making it ideal for macro photography of the anemones and zoanthids.

It is also a good choice for new divers wanting their first taste of swim-throughs in forgiving conditions. Access is by boat only, but the run from Tinderbox is short, and the site is rarely visited, so the invertebrates are undisturbed. Treat the soft rock gently; it crumbles easily and the growth on it is fragile.

The northern channel is also a good place to see the effects of the Tinderbox reserve across the water: fish and lobster densities on protected and fished reefs make an interesting comparison. Bring a torch even on a bright day to bring out the colour in the caves, and a macro lens for the zoanthids. Divers staying on North Bruny near Dennes Point can reach the site quickly by small boat, and it is a sensible second dive after a longer run elsewhere in the channel.

Boat access. The Marine Life Network guide suggests launching from Tinderbox (Fergusson Avenue ramp, low tide only; larger boats use Dru Point at Margate), a short run across the northern channel to North Bruny's western shore near Trumpeter Bay, about 10-15 minutes. Alternatively take the Bruny ferry from Kettering and launch at Dennes Point.

Anchor in sand off the cliffs. Tinderbox has a small car park; fuel and supplies are in Kingston and Margate.

The D'Entrecasteaux Channel is sheltered from ocean swell by Bruny Island, but strong northerly and southerly winds funnel along it and raise a steep chop. Southerly swell entering from the Southern Ocean affects the southern channel sites. Visibility is moderate and often green-tinged from Huon River and local runoff, dropping after heavy rain; the Marine Life Network notes a possible slow tidal current at some sites.

Calm mornings in late summer and autumn are best; the channel can be dived year-round. North Bruny's western shore faces west and is exposed to westerly winds across the channel.

Stay in the shallows at 3-6 m along the base of the soft cliffs, exploring the caves, cracks and swim-throughs slowly with a torch. The deeper flat bottom at 15 m has little to see.

Underwater Adventures Tasmania – Channel and Bruny boat trips from Hobart; otherwise private boats from channel ramps (Kettering, Woodbridge, Middleton, Gordon, Alonnah).