Water keeps getting in my manual trans. How?

This question is concerning my 96 with the T5.on several different occasions,it's rained here so hard,the road couldn't drain the runoff water fast enough.Well,as you pretty much guessed,water is getting in my transmission.I've had to drain it and refill the thing several times in the past 4 years.I get that strawberry milkshake fluid and sticking or grinding gears.So how in the hell is water getting in? Could it be the fluid vent? if so,where is the vent and how can I stop this from happening? No,iM not running through swamps or going boating with my stang .The rains are just heavy here at times.

The seal on the trans tail shaft is leaking somewhat.I replaced it 2 years ago and had damaged it trying to get the dumb thing wedges in all the way.I put sealant on it (yeah dumb) whch helped for awhile.I dont see water getting through there as its covered by the driveshaft.No other leaks.Unless it can get in through the clutch opening..