2 Pcs Waterproof Phone Pouch, [Up to 10" Large] Universal IPX8 Waterproof Cell Phone Case Dry Bag with Lanyard for iPhone 16 Pro Max/16E/15/14/13,Galaxy S25 Ultra/S24/S23 for Vacation -Black

I use these. There are many brands making similar styles, but this style of bag I've found definitely works the best and this exact listing is the perfect size for a Kindle Paperwhite 10th gen. Like it fits exactly perfectly as if it was made for the Kindle. I wouldn't like chuck it in the deep end or anything, but they've served me well in reading in the pool for several years and the bags have never leaked, plus it comes with a lanyard to put it around your neck so you can keep your hands free getting in and out of the pool.