Meet the site
The Boomer is a small rocky dome in Mary Ann Bay, rated 5 out of 10 by the Marine Life Network guide as an easy, relaxing dive in calm weather. It breaks in all but the calmest conditions (hence the name) and offers some shelter from easterlies, with shallow depths of 3-9 m and an unusual variety of short green and brown algae. Wrasse, magpie perch and leatherjackets shelter in the crevices, and there are small abalone. It becomes murky in any swell. The Leven Scuba Club includes it among the Rocky Cape sites. Local divers typically combine two or three Rocky Cape and Sisters Island sites in a day, choosing the side of the cape that suits the wind and the state of the tide.
The Rocky Cape and Sisters Island area is, in the Leven Scuba Club's words, the best collection of dive sites on the north-west coast. The quartzite of Rocky Cape - some of the oldest rock in Tasmania - forms gutters, ledges, caves and bommies, and the tidal flow along Bass Strait keeps sponges, gorgonians, sea pens and bryozoans well fed. Michael McFadyen, diving here in February 2008, recorded 18-19 °C water and 20-25 m visibility, figures that surprise divers used to the east coast.
Rocky Cape National Park also protects Aboriginal cave sites and coastal heath above the water, and a Parks Pass is required for vehicles. The nearest hyperbaric chamber is the Royal Hobart Hospital, about four hours' drive away, so conservative profiles and oxygen on the boat are essential.
What you might see
Wrasse, magpie perch, leatherjackets, small abalone, short green and brown algae
Location
A small rocky dome in Mary Ann Bay off the western rocky point of Rocky Cape, which breaks in all but the calmest weather.
Facilities nearby
Rocky Cape National Park: day-use areas, toilets and picnic facilities at Mary Ann Bay/western end and near the lighthouse road; no shops. Sisters Beach and Boat Harbour have small general stores; Wynyard for all services. No confirmed air fills on the coast - Launceston is the reliable option.
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
marinelife.org.aulevenscubaclub.com.auRecord updated 26 Sept 2026. Source claims are being reviewed.