LifeProof Fre (waterproof)
The Google Pixel 2 and Pixel 2 XL are IP67 dust and water-resistant. That means the phone can go under around 3 ft of water for 20-30 minutes and still work after. It isn't the best water-resistant rating on the market, but it's good enough.
However, if you're an outdoorsy type of person that really needs some absolute water resistance, consider Lifeproof. They're the leading iPhone waterproof case maker and for good reason.
The LifeProof Fre allows Pixel 2 XL owners to take the phone off the beaten path, into the wilderness, and on streams or lakes. Use it without worrying about the phone getting wet because it's waterproof. Capable of going under nearly 7ft of water for over an hour, if not longer. They also sell tons of mounts so you can take your phone anywhere your heart desires.