It's actually a very low aspect lug sail. We've got a little lug-rigged boat. It's a convenient rig in many ways. There's a huge fleet of International 12 Foot Dinghies, clinker built lugs designed in 1913, in Europe. They are lots of fun to sail; the Dutch require the boats to still be made in mahogany but the Italians have grp boats with cool Harken fittings
The square sail seemed to be the fastest up wind
What class insignia is that, is it a Thong or is it a Flip Flop?
I think this was a lug rigged vessel as well.
www.marinerescuensw.com.au/news-media/news/hypothermia-near-miss-prompts-warning-from-marine-rescue-nsw/
Those boats are from a group called Sydney Raid. They cruise and overnight on small trailable dinghys in different locations.
www.facebook.com/groups/raidsydney
Paul who owns the Scuffie and other members do great videos about the trips.
If you enjoy small dinghy cruising its definately worth a look. The group is big on restoring / building timber boats.
This video is about the group you photographed.