Well after a minor catapult today I got back to my kit to find the board upside down and the mast pointing straight down to the bottom. couldn't flip the board as it would get halfway then the mast would stop it(being a very wide board didn't help) couldn't move the rig from its downwards position so after what seemed like hours of trying to fix it I decided just to sit and wait for something to happen. eventually drifted into shallower water and the mast tip hit the bottom and started to swing back up enough for me to be able to flip the board and get going again.
What a pain in the arse

Unfortunately you just have to swim the board backwards against the current, had it once offshore with a race sail, took a heap of work and energy to dig it out.