Just opened a letter from the Denver TH Association.   It is a copy of the pool rules. 
One states:
"Swimming suits (not cut-offs or tennis attire) are required when using the pool.   "Solo" swimming and nudity is prohibited.  No incontinent persons with pampers/diapers are allowed in the pool." (sic)
What the heck is "Solo" swimming?  Swimming in the pool by yourself?  Since it is lumped in with apparel/nudity, I am thinking it has to be related to that.  
I have googled it,  and all I have found is that whatever it is also prohibited at the pool at Mandalay Bay.