All clothes provide UV protection - that's why you get strap marks and don't tend to burn under your t-shirt, because you are protected by your clothes. The tighter a weave is, the more protection it will offer you. Remember that the weave of a fabric may become looser when it is wet. Clothes which state their UV protection haven't been coated or anything but they have been tested to see how much protection they offer. So unless you can find the information on the particular item that is on ebay you won't know what sort of protection it has been tested to provide.