On a scale of 0-10, with 0 being not wet at all and 10 being drenched, the wetness factor of the water rides are:
- Boat cruise across the lake: 10
- Jurassic River Ride: 3
- Log flume ride: 7
- Bilge Rat Barges: 11

Jurassic River Ride splashes. In the log flume, you get spray and then sometimes water comes over the top. My friend got drenched on the top, but her shorts were dry.
The bilge rat barges can soak you. Huge waves of water come over the side, and those can get your lower half. Plus, they go under waterfalls at 2-3 points, and if you're caught under the waterfall... well, you're drenched. There is, however, a spot at the center of the boat that remains dry, where you can put your shoes and socks, and anything else that needs to keep dry.
Incidentally, though you look silly, a rain poncho will keep you pretty dry. You can bring your own for cheap, or buy yellow ones there for six bucks. I bought one there. It kept me high and dry on the log flume, and would have kept me dry on the barges except for the fact that it was open a little on the side, and a big wave got half of my shorts wet.