We were about to write about Watershot's housing for the iPhone, and then we found something else - the iGills. They're both housings that let you use your iPhone underwater. However, unlike the Watershot, the iGills turns your iPhone into more than just an underwater camera for taking pictures and videos - you still can't make calls underwater or use other apps, but it also turns your iPhone into a smart diving computer, a flashlight, a compass, and dive log.
Unfortunately, the iGills is not available for the iPhone 5 at the moment so if you're an iPhone 5 user, you should go for the Watershot instead, especially if you intend to use it as an underwater camera only. The depth rating for the regular version of the Watershot and the iGills is 130ft (40m). The Pro version of Watershot can go down to 190ft(60m). It's important to note that these two are not casings, they're housings. If you're looking for a waterproof casing for the iPhone, check out Lifeproof.