Video: Traditional Perth Australia Day Swan River raft-up erupts into ugly brawl on sand-bar

The raft-up is a common sight on Australia Day on the Swan River - what’s uncommon are the ugly scenes that broke out in the water on Friday.

Raft-ups involve a group of boat owners tossing a line to connect or dropping anchor along a sandbar and usually have a party vibe.

Rocky Bay near Mosman Park did not pass the vibe check this Australia Day though.

The video shared on social media showed more than 20 boats anchored on a sand bank when dozens of people began rushing to brawl in the shallow water.

Dozens of shirtless young men were captured running to join to melee while pushing, shoving and throwing punches.

It’s not clear what sparked the violence but footage of the skirmish continues for more than a minute.

Social media users had a field day in the comments of the video.

“It’s not Australia Day without a few fights,” one said.

“Where are the bull sharks when you need em,” another added.

“Somebody forgot the words to Khe Sanh,” a third joked.

Police said they did not attend the melee.