i put my phone in a ziplock bag inside of a good water tight pocket on my pants.. s'all good
I have a Galaxy as well, and I also use a ziplock. If you use the sandwich bags (as opposed to the freezer bags) you can actually control your phone and have a conversation without taking it out of the bag.
I also have a case for my phone, so I don't know about durability if you hug a tree at speed...
Carry mine for boarding as well for tunes. It can also be used for emergencies situations as well. I have an Otterbox for the phone so it can take a bit of a beating and adds some waterproofing as well.