Hello Grunt, Good to see Ya here !
I don't think You would have much of a problem with the battery "shorting out" under the seat as long as You use a sealed battery. IMO water isn't the killer on a battery, it's grease and dirt on top of a battery that can cause a draw and kill a battery. Most UTV's run an AGM battery now and a lot of people submerge them quite often (even in the stock location) !
Hope this helps !