I supect the only thing to do is:
- slow down
- try to keep your feet as far away from the water as possible (so your peddles are parallel with the ground)
- go back to being a kid and stick your feet out in front of you
- or just get wet
Of course the big extra danger here is that if you haven't got a rear mudguard, the water will go all over your back and your bags, if you have them. The answer? Sadly inevitable - get a rear mudguard. Although I've singularly failed to take my own advice so far.