Lots of dry bags come with external pockets but none of them are waterproof. Which I don’t think it makes a lot of sense. If you have a bag with it’s main purpose to stop water from getting in and keeping your times dry then a pocket on this bag should do the same. This is why I really like the DryTide 30 liter dry bag/backpack. It has an external pocket for your phone and things like that and the pocket is waterproof. So if you are kayaking the Adriatic sea coastline or doing multi day sup trips, surf trips, if you spend your days at the beach, hiking in rain etc… this might be the perfect bag for you.
Here is a short video where the waterproof external pocket is tested: