A leash is a foundational surf accessory. Don't be "that guy" who's board is everywhere but under his feet. Keeping it close by when you bail isn't just for the convenience of not having to swim after it, it also prevents it from being firmly lodged in someones forehead as it careens through the lineup. Just get one please. Shoot for a leash the same size as your board. If you fall in between sizes, go shorter unless you plan on noseriding.