For hiring, try Sailboard Headquarters in Sandringham (
www.shq.com.au/) or Zu Boardsports in St. Kilda (
www.thezu.com.au/).
If you want to sail in the Bay, also find out where Green Point and Rickett's Point/Beaumaris Life Saving Club are located. Parking fees are $15.50 for the day at both locations, but a ticket from one will be accepted at the other location.
Just looked at the SB forecast: brown arrows at 12.00pm on Saturday night. If it weren't for the Noah's

I'd be there.