how long would it take?
Any issues with boats and marine traffic?

Have done the trip from Pt Ormond to Williamstown on a sailboard, and back.

maybe 20 mins. and in a Northerly.

The only problem would be a gear failure in the shipping channel, so have a spotter and make sure you are complying with all boating regs so spotter can call the water police.

No laws against navigating the stretch, but I can see a stack of on spot fines they will be looking to hand out once they have you on board.

a sailboarder at Pt Ormond broke a uni joint and got rescued by water police. as they dropped him and his kit off at beach he got handed a fine for not wearing a life jacket.
there were over 10 others sailing right there and past the police boat all without life jackets and never given a second thought.
must be their way of getting petrol money.