Andrew, if you look closely in the middle picture above, you will see the Skipper is standing on a springboard. During the tack, as the boat passes head to wind, he "Jumps" on the board and is launched to the other side. I think he's also wearing a harness and a sort of trap wire arrangement, just in case he doesn't make it on the first jump...

Under the tarp is a net, to catch him should the trap wire break.