Roop, you're too nice a guy to have to drag a pond for. What ever you do, don't kayak with your waders on!!!
I've never tried it, but, I'd have to imagine you could take on enough water to counteract the bouyancy of a pfd. In a deep water situation you are guaranteed that the top of your waders will be below the surface of the water even with a pfd on.
Also, wading belt or not, water will get into your waders gradually. I've seen someone in real danger after falling out of a kayak, and he had shorts on. He spent a solid half hour trying to get back into his yak. They sent the Fire/Rescue squad out after him becuase of hypothermia. You won't be getting back into your yak in deep water unless you have deck rigging, your paddle, and a paddle float(all of which should always be in your yak anyway). Also, the extra weight of the water in your waders would most assuredly make hauling your butt into the kayak impossible.
Next summer, when it's 90 out and you are with friends, put your waders on in someone's pool and try to get back in your kayak. It's an awful big gamble to take, especially if you are going to be alone on the water. We just had a perfectly healthy 22 year old guy drown in Weymouth, and he was with two other guys in a canoe, and none had waders on.
Get some waterproof pants to wear in the yak over fleece.