Everyone remembers the towel. Almost everyone remembers sunscreen, at least in theory. It’s the second-tier items, the ones that don’t make the mental checklist until you’re already squinting at the water, that tend to turn a good beach day into a slightly uncomfortable one. None of these are exotic requirements; they’re just easy to overlook until the moment you actually need them.None of what follows requires a special trip to prepare for. It’s mostly a…