During the summer I like my hair to be as low maintenance as possible. I usually let my hair dry into somewhat messy, beachy waves. This homemade recipe works, but fekkai & bumble and bumble have their own bottled surf sprays as well. During the summer it's easy to just go with the flow than to fight the humidity. The less product and styling, the better your hair will hold up in the summer heat.
Check out this kitschy "vintage" ELLE 2004 Doutzen Kroes editorial for more surfer girl inspiration. The day-glo colored surfwear is pretty kooky.