Remember that you will have limited space to store all of your stuff, so pack efficiently. Bring layers that you can wear for different purposes and repeatedly. Think layers -- t-shirts, which you can wear with a long-sleeved button-down shirt (e.g. Columbia PFG shirts, which I've been known to wear in the water as well, for warmth and sun-protection), to which you can add a fleece or other outer wrap. Also a pair of nylon or other quick-drying pants. You won't want jeans because they are heavy and once wet will not dry. You only really need one of each of these (try a color that goes with all of your other stuff, if you care), since they can be rinsed and hung out on the lifelines to dry.

You might luck out and have gloriously warm weather during your entire trip. Or you might get caught in a cold front or two. Regardless, it's the most beautiful water you'll ever see.