You need a bag that can handle the salt, sand, and wet gear. Key features include a separate waterproof compartment for your wetsuit or soggy trunks, drainage grommets, and durable, easy-clean materials. Look for extra pockets for wax, a fin key, and your phone/keys. A good surf backpack keeps your dry stuff dry and your wet stuff contained, making the trek from the car to the breakway cleaner and more organized. Function over fashion, but many look slick too.