LifeProof Fre iPhone X Case - Waterproof
The iPhone X is water-resistant, but if you plan to actually take your new iPhone into the pool or ocean on purpose you'll want to invest in a waterproof case that provides added seals.
LifeProof offers a waterproof iPhone X case for pre-order that will protect your phone from drops, dust, snow and water up to 6.6 feet for an hour. This adds a lot of water protection you don't get with the naked iPhone X, and unlike the built-in protection the LifeProof iPhone x waterproofing won't fade over time.
$89.99 at Lifeproof
*iPhone 7 case shown as example.