Ditto Greg as usual. I hardly ever don't wear a PFD and then only on hot, still days, relatively short distance. On warmer days I wear the Mocke PFD which is pretty cool. For extended distances I take my waterproof mobile (which is attached to me, not the ski) and always inform my husband of my course and expected return.
I have discovered a fantastic cooling fabric, unintentionally designed as such by Ground Effect in New Zealand. It has an internal single layer of merino and outer layer of polyester. I originally bought it as a base layer for running on cold rainy days but found it was freezing cold, especially when wet. On the water, it is cooling when wet, like a rashie, but maintains the cooling effect many times longer, probably because the merino slows the rate of evaporation. Once completely wet, it will keep me very cool for at least 90 minutes on a 30 degree day. I haven't tried it for longer or hotter yet, but I'm sure a quick splash on the arms would be more than enough to maintain the refrigeration.
Past skis: Spirit PRS, EpicV10Sport Performance, Epic V10 Elite, Stellar SES Advantage. Current skis: Fenn Elite Spark, Fenn Swordfish vacuum. Custom Horizon, Epic V7