My daughter had some issues getting this case on... but once we did, it has worked amazingly. No issues overheating. No problems connecting cables. We won't "underwater" test this, but she took it to the beach for a week and the water/sand stayed out of the phone!
find this on Amazon: http://amzn.to/2aJVqQ2
Sunwukin Waterproof Case for iPhone 6s Plus/6 Plus 5.5 Inch IP68 6.6ft Underwater Shock Snow Dirt Poof Protection Cell Phone Cover [Grass Blue]
I received this case free in exchange for my honest opinion. For the price.. it is definitely worth it :)