Both the Revo and Adventure seats are at or below the waterline, so they have scupper plugs to keep the seat area dry. This works great in most cases, but in more active water, you can find yourself sitting in a puddle.
So if you need to drain water, you can simply reach down and loosen one by hand (it won't fall out). You can keep this area scavenged by simply taping (clear packing tape works fine) over the forward 3/4 of your scupper holes from underneath -- looks like these:
Thanks to Mr. Bernoulli, the water moving past the tape will suck the water out of your seat area!
Basically, if it's calm, I leave both scuppers closed. If I take on water or expect to get a wet seat, I open one part way and let it slowly suck out the water as I move along. That way, it won't come rushing in too quickly if I stop. Experiment and see what works best for you.