We were there several weeks ago, and I don't recall seeing people with chairs, though I could be wrong. However, there's at least one booth there that rents an assortment of equipment, and they might have them. It is not a huge beach, but is very lovely. You could e-mail the Coki Beach Dive Club and ask about the chairs; they don't have them, but they are very nice folks who would almost certainly know the answer and get back to you.