Butts Reef sits in the middle of the Huon River mouth, south of Charlotte Cove, marked by two poles. The Marine Life Network guide describes a reef top about the size of a football field, a flat weed garden with a few small bommies, and sharp drops on the western and southern sides, in 8-15 m. It lists crayweed, strapweed and delicate brown algae, and suggests the site is good for practising boat-handling skills, presumably because of the markers and the need to anchor carefully off the reef.

The drop-offs are the most interesting part: the faces shelter fish and invertebrates, and in the dim, tannin-stained Huon water sponges and other filter feeders may grow at shallower depths than usual, as at Ninepin Point. Wrasse, leatherjackets, magpie morwong and other reef fish frequent the edges, and rock lobster may be found under ledges. The weed garden on top provides habitat for small fish, weedy seadragons and invertebrates.

Visibility is usually modest and falls after rain. It is a quiet, rarely visited reef suited to divers with a small boat in the Huon area, and it can be combined with Charlotte Cove or Ninepin Point. Carry a torch and a compass, and avoid anchoring on the reef.

The Huon mouth also carries salmon and mussel aquaculture, so check charts and keep clear of leases and their moorings. The tannin layer makes the reef top noticeably darker than surface light suggests, so make sure every diver has a torch and stays close to a buddy.

Boat access. The Marine Life Network guide suggests launching from the Charlotte Cove ramp (small dinghies only) or another Huon ramp such as Cygnet or Verona Sands; the reef is marked by two poles in the middle of the Huon mouth, a few minutes' run. Anchor in sand off the reef edge, not on the weed garden.

Launching at Charlotte Cove is only practical for small dinghies; Cygnet has a better ramp.

The Huon River mouth and lower D'Entrecasteaux Channel are sheltered from ocean swell by Bruny Island, but northerly and southerly winds funnel along the channel and raise a steep chop. The dominant influence is the Huon River: its tannin-stained, fresher water forms a dark surface layer that cuts light, especially after rain, when visibility can drop to 1-3 m. After dry spells visibility may reach 8-10 m beneath the tannin layer.

Tidal currents are mostly mild. Late summer and autumn, after dry weather, are best; the area can be dived year-round.

Descend near one of the marker poles onto the reef top at about 8 m, cross the weed garden to the western or southern edge and drop down the face to 15 m, then follow it along before returning to the top.

No regular operator; private boats and club divers.