Don't box yourself in...I bought this to wear with jeans and a tank top not a swimsuit. Im 66 years old, 54 and 150 lbs. I purchased an XL and it fits perfectly. Lots of room and great length for me falling 5-6 below crotch. It is synthetic, lightweight and nice flow for hot Texas days and nights. I would have liked pockets, but then I like pockets in everything. Fast delivery and the color is as pictured. I love it.