Dogs and swimming pools?

What are the risks of letting my dog swim in our swimming pool? Other than the obvious drowning. I am curious because we swim in our pool at least one hour a day with our 10 month old Boxer/Pit bull mix. He seems to ingest a lot of the water; is this a hazard to his long term health? (Liver and kidneys). Should I limit his exposure? Or should I just let him enjoy this amenity?