I have just stained my deck. Can I apply a water sealer over top?

I have stained my deck before. After 2 years, it had a lot of green mold growing from a very wet spring. I cleaned it thoroughly with soap and water, scrubbing and then a spray on deck cleaner. I had planned just to use water seal, but the cleaning removed some of the stain. I applied the same stain with sealer that I used before. I have a clear water sealer that I would like to put over top to protect the deck. It takes a lot of sun in areas and the spring can be very wet. Can I put a water sealer over a stain? How long should I wait to apply the sealer?