Thanks for the feedback guys.
@myusernam: Regarding the boards, seems like a good idea when away from land/boat. For me I've always enjoyed keeping my spearing simple, chuck the gun in the car and I'm good to go. The board seems to take it to the next level and another toy I need put in the car and wash and store in the garage.
@Salties: I didn't think of whitworths, good idea for the ropes/connections. I had a quick look, couldn't see actual spearfishing floats etc. but if it was cheaper I could tow a mooring buoy around!

(not cheaper though, those foam filled ones are $90!)