A ziplock bag is all you need.

Yes, it’s that simple. A sandwich or quart-sized ziplock bag will keep your phone and keys dry and sand-free. Just squeeze the air out before sealing. You probably already have one in the kitchen.

If you’re worried about dropping it in the water and actually submerging it, get a dedicated waterproof phone pouch for $10. But for normal beach use—sweating, splashing, sandy pockets—a ziplock is over-engineered in a good way.

Keys go in the same bag. Or a separate one. Doesn’t matter.

Don’t overthink it.