Meet the site
South Brig Rock is a small island near Grassy that the Marine Life Network guide rates 7 out of 10. Its eastern side is surrounded by sunken outcrops, with shallow rocks at about 5 m that are good for crayfish, challenging swim-throughs close to the island and deeper, safer water further out on the rocks to 18 m. Cracks support gorgonian fans and small marine life, and the seaweed growth is luxuriant.
The guide describes very large crayfish of 3.5-4.5 kg and notes that they fight hard. Sea sweep, old wives and long-snouted boarfish are the common fish. The site is popular in westerly weather, but the exposed rocks pound in heavy swell.
King Island's reefs are best known to divers for their crayfish, which grow large in the cool, nutrient-rich Bass Strait water, and for sandstone and granite ledges covered in gorgonians, zoanthids and sponges. The Marine Life Network descriptions date from when King Island Dive Charters operated from Grassy; with no current operator, these sites are now visited only by divers who organise their own boat, and fishing pressure has reduced crayfish numbers since.
Recreational rock lobster and abalone fishing in Tasmanian waters needs a licence and is subject to seasons, size and bag limits. The east coast around Grassy is the reliable side of the island when westerly swell closes the west coast, and the island's lack of a chamber means aeromedical evacuation for any diving injury, so conservative dives are the rule.
This is a site for self-sufficient visiting divers with their own boat and a local contact; there is no one on the island currently guiding dives here, and the position given is an estimate from the published description.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
South Brig Rock (Grassy) is recorded as Island in King Island. The listed access is boat (day trip). Confirm the actual meeting point, route and permission to visit; a map pin does not establish any of these.
Topics flagged by the stored research
These are questions prompted by the existing notes, not a verified or complete hazard assessment.
- Water movement
- Ask how swell and local exposure affect the proposed entry, exit and route.
Historical access notes exist for this record, but have not been independently verified for current use. Request current directions from the operator or site manager rather than following an old entry description.
Questions, answered
Is South Brig Rock (Grassy) suitable for my certification?
The record lists Open Water. That does not establish suitability for every route or day. Share your training, recent experience and equipment needs with the operator and ask about the specific proposed dive.
Can I book South Brig Rock (Grassy) through YouDive?
YouDive is an independent research directory. Contact an operator directly to confirm whether it currently runs the trip, the inclusions and the booking terms.
What you might see
Crayfish (large), gorgonian fans, sea sweep, old wife, long-snouted boarfish, luxuriant seaweed
Location
A small island near Grassy Harbour whose eastern side is surrounded by sunken outcrops, with swim-throughs near the island and deeper rocks further out.
Facilities nearby
Grassy: harbour, boat ramp, small shop/accommodation. Currie: supermarket, cafes, fuel, accommodation, King Island Historical Museum (lighthouse keeper's cottage), hospital (no chamber). Grassy: harbour and boat ramp. No confirmed public air-fill station - arrange locally.
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.auRecord updated 26 Sept 2026. Source claims are being reviewed.