If you want to use your iPhone camera underwater, the Optrix PhotoProX case and lenses for the iPhone 5/5s are going to get the job done and protect your phone. The set sells for $149.95 direct with free shipping.
Testing waterproof products is always a leap of faith. There's a lot that can go wrong and there's not really a "testing-related phone accident" clause in my employment agreement. Optrix advertises "Military-grade" protection and IPX8 water immersion protection. Once I made the commitment, the case was 100% effective through my testing.
The underwater photos were of excellent quality. That's what the water in the Gulf of Mexico looks like this time of year, which is why folks like to vacation in Hawaii.
The set comes with four lenses: a Low Profile 0° for no effects, a Macro lens for closeups, a Fisheye and a Telephoto 2X. There's a carrying case, a set of O-Rings (required if you want the waterproofing to work), a wrist strap and a cleaning cloth. There's an Ultimate bundle for $199.95 that adds a two more lenses: a Telephoto 4X and a Wide 165° lens. There are other accessories including a tripod, a monopod and a floating wrist strap.
Optrix hasn't yet made any announcements about new cases for the iPhone 6 or 6+, but here's guessing that they'll announce something soon and that there will be a case-only option for folks who already own the current versions.
Using an underwater phone case isn't for the easily spooked. You're using a $600+ piece of gear in the environment that's most likely to destroy it. The Optrix has earned my trust. It's definitely worth a look if you're interested in underwater photography and don't want to spring for a GoPro or a dedicated waterproof camera.