If you're not in the front row, you probably won't get very wet.
The last time I was on it, I was in the front row, and I got every bit as wet as on Kali (a ride that I now avoid specifically because of that!!). You should have seen the look of horror on the college-age girl's face who was going to be getting into my seat.
I've been to Disney in January on my last 2 trips, so I was unable to ride Splash. But if I ever go back when the ride is open, I will most definitely request not to be in the front row.