Not every time, but the lake water definitely makes my allergies go crazy some times.
I get seasonal allergies sometimes even without the lake water and the usual suspects of antihistamines work pretty well, claritin, allegra, zyrtec, benadryl in that order of effectiveness for killing the allergies and also in that order for how much they'll put you to sleep.
Also if you just have drainage pseudofed works pretty well and doesn't cause drowsiness. Get the good stuff that you have to go to the pharmacy counter to get, not the "PE" stuff they have on the shelf. It will do nothing for itchiness caused by allergies, but it will dry up drainage really well. Has a little it of a "caffeine" type of effect but (for me) very mild.