Here is a kit that lets you take your smartphone underwater to capture video. Optrix for iPhone 6s is waterproof to 33 feet and drop tested to 20 feet. It transforms your smartphone into an adventure camera you can take anywhere. You also get wide-angle, telephoto, and other lenses.
This iPhone 6s case has a crush resistant unibody body. It is fully mountable and compatible with various accessories. More information is available here.