All pools in Salt Lake close the same weekend every year... Labor Day. I agree that it would be nice if they would stay open longer since we do generally have nice weather past Labor Day but I've yet to see any pool (lifeguards or swim at your own risk) stay open past that date here.
As for the 8pm closure... they sent out an e-mail several weeks ago. You may want to check to see if you're on the mailing list.
Lastly... the boats do stay open longer... yea! I don't remember when they shut down but I believe its through september. Hope that helps!