I've got a Samsung Xcover pro. It has an easily removable back plate and a replaceable battery and is IP-68 rated. My old Casio was in the same vein. Maybe y

I've got a Samsung Xcover pro. It has an easily removable back plate and a replaceable battery and is IP-68 rated. My old Casio was in the same vein. Maybe you couldn't get it quite as thin, but they did away with the easily removable battery long before they started trying to waterproof it.