Rash Guards have evolved from the old days of tight fitting, no stretch, and no breathability into a whole new world. The AKONA considers them Sun Shirts today. What ís the difference? The Sun Shirts today are made with much lighter weight materials, with more stretch and flex, and have significantly more breathability. In short, they are so much more comfortable, they can be used for any water sport of you choosing or just sitting in sun all day long at the beach or on a boat.