Thanks to some good advice on here I got myself a Camelbak last week. And I have to say it's one of the smartest purchases I've made for windsurfing. I got the Camelbak Rouge- which is a 2 litre capacity model- and used it for the first time sailing Town Green at Port Macquarie a few days back. It was sunny, warm (30 degs) and a long way from the nearest tap. At first I thought, "Great, another bloody thing I got to cart around", but I ended up totally forgetting it was on my back. Not once did it slip, move or annoy me, and surpringly I drank a litre of water in only a 2 hour run.
So, if you've contemplated buying a backpack for water and a little storage, but thought in some way they'd be a hassle or would effect your sailing, don't fear, they are as snug as an impact vest. You will totally forget you have it on, and once you feel your mouth drying out, you'll be so greatful a nice drink is only inches away. This one little thing is going to make life so much easier this summer. I'll now be able to rack up more kays per outing which is sure to improve my over-all sailing skills.