Hi Frozen,
check out www.speedsailing.co.za

lots of pics, and if you scroll down to the bottom of their homepage, a link to cool video footage from a previous event, with some interesting wipeouts in ankle-deep water.

Have to agree with Wouter, we seem to THINK spinnakers have made beachcats faster. What we forget is that it may make their VMG from A to C mark faster, but that`s because it keeps the apparent wind well forward even when reaching deep downwind angles, something not possible without the spinnaker, so instead of gybing 45 degree angles downwind and covering more distance in the process, we can sail straight to C mark with maybe a short gybe or two, reducing the distance covered substantially, so we appear faster downwind. But a boat without spinnaker reaching the old way gybing on 90deg laylines might actually be sailing faster, he just has to sail further..
Since beam-reaching up and down does nothing to assist your progress from A to C mark, very few of us do much of it, but I`d bet it is faster than a spinnaker ride on many boats. (And the pitchpoles are way more spectacular !)