there are ways to do it, do a search on here about waterproofing batteries and you will find many hits. they use products like plastidip and liquid tape, they work well for batteries. also max amps sells their lipo's as 'waterproof'. i put that in quotes because i have never submerged them in water. if you cant find anything ill point you in the right direction. in fact i started a thread on here about waterproofing in the off road electric section. youll get a hailstorm of input, everyone has there own way and everyone elses way sucks so take them with a grain of salt and make your best informed decision!!

let me know if you need more info