­The JW Marriott Cancun Resort & Spa looks and feels like a JW anywhere in the world: polished, accommodating, understated. You can count on a copy of USA Today being delivered to your room every morning along with your freshly polished shoes. However, take a look out the windows of any of the 448 rooms (all have water views) and the signature aquamarine blue of the Caribbean reminds you exactly where you are.

Your head instantly fills with dreams of cool swims, warm sun and cold drinks—all easily fulfilled by the resort’s four pools, pool bar and 700 feet of brand new, shockingly white beach, part of a reconstruction project that used thousands of cubic meters of new sand to enlarge and shore up more than five miles of...