Staying warm on the water can be a challenge, but when you keep your head warm the rest of you stays warmer too! These neoprene beanies from Ion will help keep you warm on the coldest of days. Wear it windsurfing or kiting, wear it on the beach - they are stretchy, warm, and comfy and stay on even when you fall down! They also include Ion's Loser_Leash allowing you to tie your beanie to your wetsuit zipper so you can keep your beanie safe on the water.
Sizes run similar to helmet (bike or ski) sizing. Stretchy, so a little forgiving on size.