I wouldn't recommend this as summer entertainment. The iPhone in question had a tight rubber case, and my guess is while the video did record OK, the moisture in the phone will eventually take a toll.
There are a few water-tight cases for the iPhone, and we road tested an Otterbox Defender case back in April. Perhaps this fellow will invest in such a case should he go iPhone diving in the future.
Now of course the video might be a fake (I would have expected to see water on the lens for example), but at least it's an entertaining weekend diversion. Click through to the second half of the post to see the video.
Via Cult of Mac. The pool drop, in all its glory: