Ah, pool party season in Vegas. Four months of drunken, half naked people spending too much money to dance next to a pool before swapping STDs.
The day-club concept was originated at The Hard Rock with their Rehab pool party, which became so popular that they based a reality show on the event. Seeing the opportunity to separate idiots from their money, many other resorts on and near The Strip launched their own pool party events.
I don't know how to state this more strongly: avoid the Vegas pool party scene like the plague (especially since you just might get the plague if you go into a pool with some of the people in those crowds).
These events are the definition of stupid Vegas excess. The crowds are made up of douchey people with toned bodies who will make you feel insecure about the fact that you've been avoiding a trip to the gym for more than a month. Everything is overpriced (not uncommon for anything in Vegas) and just like in a nightclub, it's nearly impossible to find a seat if you haven't paid through the teeth for bottle service. Some of the bottle service options include private cabanas where you can get your own flatscreen TVs... making anybody who pays for one clearly the king of the d-bags.
Why pay an expensive cover charge to enter one of these hellish petri dishes of depravity when you can just hang out poolside at your hotel for free without having to deal with the same auto-tuned dance tracks that every DJ in town insists on playing. The Mandalay Bay pool area has a fake beach, a lazy river and a wave pool... which is way more awesome than a nightclub atmosphere moved outside into the glaring light of the sun. I mean, I'll rock a nightclub once in awhile when I can hide in the darkness as I drink enough to dance... who needs to have their shame revealed by the daylight?
And that's the main reason you don't want to go to a Vegas pool party... because you really don't want to party with people who have no sense of shame. It's just unnatural.