Sloop Rock is a striking granite spire at The Gardens in the Bay of Fires. The Marine Life Network guide describes Inner Sloop Reef, an extensive reef near the spire in 5-10 m, rated 6 out of 10, with reef fish and schooling fish, photogenic coastal formations and a natural pool and picnic facilities nearby. It can be reached by boat or by an extended surface swim from shore.

The spire makes a memorable landmark above water, and the reef around it is a pleasant shallow dive when the sea is calm.

It suits Open Water divers with boat support, or fit shore divers happy with a long surface swim.

The north-east coast from St Helens to the Bay of Fires is built of the same orange-lichen granite as Freycinet, and under water it forms rounded boulders, cracks and swim-throughs. The regional guide notes damage from the long-spined black sea urchin (Centrostephanus rodgersii) on several sites; this urchin has spread south with the warming East Australian Current and grazes kelp and weed down to bare 'barrens', so expect patches of bare rock among the weed.

The north-east sees far fewer divers than Bicheno or the Tasman Peninsula. There is no regular charter boat, so most diving is done by Launceston club members and visitors towing their own boats, and conditions are checked on the morning rather than booked in advance. The nearest hyperbaric chamber is the Royal Hobart Hospital, more than three hours' drive away; Launceston General Hospital has no chamber, so evacuation planning and oxygen on board matter here.

From St Helens take Binalong Bay Road and the Gardens Road north to The Gardens and the Sloop Rock area (about 25 minutes). Park at the Sloop Rock lookout or picnic area; the reef can be reached by an extended surface swim from shore. Boats launch at Binalong Bay, about 10 minutes south.

Allow about 2 hours' drive from Launceston via Scottsdale or the Tasman Highway through St Marys. Park close to the water where possible and check the exit before entering; the granite is slippery when wet and swell surges can be deceptive.

The St Helens and Bay of Fires coast faces east and north-east into the Tasman Sea, so easterly and north-easterly swell over about 1.5 m, and the common summer NE sea breeze, make it rough; the Georges Bay bar breaks in easterly swell. Westerly and south-westerly winds blow offshore and give the flattest seas and clearest water. Southerly swell wraps around St Helens Point.

Visibility falls after rain when Georges Bay drains tannin-stained water on the ebb. Exposed to easterly swell; only dive in westerlies and small seas.

Descend on the inner reef at 5-6 m and explore towards 10 m around the base of the spire, watching for schooling fish, then return to the boat or swim back to shore. Turn the dive at half gas (thirds where current or overhead sections are involved), deploy an SMB before surfacing for the live-boat pick-up, and complete a 3-minute safety stop at about 5 m where depth allows.

East Coast Scuba Centre (124 Binalong Bay Road, St Helens) is listed by Wikivoyage as offering dive and snorkel equipment hire - current trading status and whether it runs boat dives are unconfirmed. Otherwise sites are dived from private boats and by Launceston clubs and Tasmanian Divers (Launceston) on occasional trips.