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

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.