Boat carrying 12 people sinks during Raft Up event on Swan River A boat has sunk in Perth's Swan River near Mosman Park. A BOAT has sunk in Perth's Swan River near Mosman Park. A boat carrying up to 12 people capsized in the river when it was tied to other vessels for the annual Raft Up event, Seven News reported. Water Police said no one was injured in the incident. People tried to stop the boat from sinking and towed it to shallow water.