The pools in Las Vegas can either be fantasy areas styled after a desert island or just a hotel pool.

If you want the full treatment, go with the prominent Strip hotel pools, the 11 acre "Beach" at Mandalay Bay comes to mind.   In such place, you will find fountains, water falls, river rafting, swim up blackjack, private (big bucks) cabana for rent, even a wave pool.   But that comes with a price, the higher price of the room.  On certain evenings, Mandalay Bay presents a Concert at the Beach on the stage area next to the wave pool.  The area can also be transformed into a private catered beach party for weddings and conventions. The large number of guests at the hotel means large crowds at the pool maybe even a line to get in, then fierce competition for deck chairs and high priced drink service not to mention the noise of the multitudes.

At the MGM Grand, you have your choice of at least four pools, including an adults only pool, a pool that attracts more swimmers, and a "river" with a pleasant current that floats you past waterfalls, under palms, and in and out of the sun. The River opens at 10am and closes sometimes as early as 5pm. The other pools open earlier and stay open later, but all the pools at the MGM are shut down by 8pm. The River is closed from October thru March! It is a very very long walk from the rooms thru the casino past the shops and restaurants to the pool area. The pools are always very crowded, which is a turn-off at first, until you've adjusted to the fact that Las Vegas is very crowded period. After a day or two, it doesn't seem to matter nearly as much.

 For a change of pace, there are the pools (6 of them) at the Bellagio Resort & Casino. This is a pool with class!  You will not see any pool noodles or water guns at this "waterpark".  The theme here is rest and relaxation.  There are an abundance of loungers and a good balance of shade and sun.  The Bellagio does not have an area for European sunbathing and the pools are shallow - no diving here (good news for families but unfortunate for others).  The landscaping looks more like a castle garden than "wet n wild". There are beautiful flowers, arbours, and tall trees to help create a very relaxing atmosphere.  

Other tropical destinations in this desert meca can be found at the Flamingo, Mirage, and Tropicana resorts.  These are older resorts but they pull out all the stops when it comes to the pool areas.  Both have large, multi-acre, "lagoon-style" pool areas complete with towering palm trees, groto waterfalls and plenty of areas for lounging.  These used to have the "Best Pool in Vegas" designation until the newer resorts came to town such as Mandalay Bay.  Both of these hotels are reasonably priced and are terrific choices for families on a budget.

Mega resorts like Caesars Palace, Paris, Planet Hollywood, Luxor, have good sized pool areas but strike a balance between Mandalay Bay and Bellagio.  The areas are open with only a few trees for shade.  Most of these pools are rectangular on shape and shallow (about 4 feet deep).  These are designed or lounging and partying for the 20-40 something crowd.   

Downtown, at many of the off-Strip hotels, and a few Strip hotels, the hotel pool is just that: a hotel pool - perhaps a rectangle of concrete with a shallow end and a deep end much as you will find in Des Moines .  (An exception is the newly renovated Golden Nugget where there is an impressive waterfall from a balcony into the pool, waterslide, etc.)  But that also comes with a much lower price for the room, a smaller number of guests at the property yielding a crowd of perhaps 6 or 10 at the pool, and little competition for deck chairs.  You have to make your own noise and bring in your own discrete drink - but, as in all pools, no glass please.

So decide if you want the waterfalls and desert Island motif and are willing to trade money and put up with the crowds, then go for it and hit those big hotel pools.   If you want a quiet retreat from the hustle and bustle, go with a smaller, not so fancy, hotel pool.

Recommend visiting this site that has virtual tours of all the Las Vegas pools: