While I'm sure fleece under a spray suit is comfortable and warm out of the water (hell, I wear fleece most of the winter regardless), it does little to nothing while you're in the water. Unless there's very little chance of something happening on the water, I think it's foolish to not wear either a wet or a dry suit in cool water / weather conditions. You never know when you could end up in the water for longer than you'd like. Even a thin 3/2mm wet suit can make the difference between life and death in cooler conditions. Now if you're out in light wind with 10 other boats around, I agree the fleece and the spray suit would be fine...