I've used this kind of waterproof pouches and they really do work flawlessly, they are incredibly convenient for trips to Sea World, Disneyland and Waterparks, however they're kinda disposable after using for a few days!
Word of caution!
No matter if you use them in water parks, pools or sea and wash them thoroughly after each use, they will eventually leak after just a few uses. So be careful and use common sense. Don't submerge them more than a few feet. They work best for splashes, pool area, rain, etc, but not under water!
Tip: Try not to take your phone in and out many times during each use. Remember, it's just a glorified sandwich bag, it uses the same kind of Ziploc (TM) to seal, but the corners (where both sides of the ZipLoc meet, degrade quickly).
My Current Devices: LG G2 32 GB, Samsung Galaxy Note (International Version), Nokia Lumia 900, (backup), Motorola Atrix 4G (GB 2.3.4)*sold*, Motorola Lapdock *sold*, Asus Transformer Tablet, Nexus One Google Phone (retired), Viewsonic G Tablet (retired), Nokia N97 40 Gb *sold*, Nokia 5530 *gave it away*, HTC Touch*died*, HTC Touch Diamond GSM*sold*, Palm Pre GSM*sold*