LAS VEGAS -- In addition to the Wheel of Fortune slots, underdressed cocktail waitresses, and overpriced room service, there's one thing every hotel on or near the Las Vegas Strip has in common: a pool. Or, in the parlance of the resort business, a ''water feature."
Not all the water features here are created equal, however. Some are inventive expanses with sandy beaches, waterfalls, and bubbly hot tubs. Others are mundane, water-filled holes in the ground that reflect little of the kitsch for which Las Vegas is famous.
For tourists, the pools in Vegas are among the most important parts of the daytime experience. So here is a guide. I took my 14-year-old ''little brother," Jamie Koch, whom I mentor through the Big Brothers Big Sisters of America program. It wasn't hard to hook Jamie on the project: His eyes sparkle when he sees a fountain at the mall.
The criteria for our summerlong ''study" of 20 pools on or near the Strip were nebulous and subjective. Mostly, we asked ourselves: Is the pool innovative? Does it fit the hotel's theme? Is it any deeper than the typical 3-to-4 feet of most of its rivals? Is it clean? Is the layout logical or clever? Does it invite us to jump in? Do the lifeguards appear to be paying attention?
Since the resorts' pools are not open to nonguests, in the majority of cases, we stopped in with friends who were staying at the hotels. But sometimes we just walked in. In theory, guests are expected to show a room key at the pool's towel desk. In some cases, however, we passed by with a smile and a nod.
The Flamingo: A+
3555 Las Vegas Blvd. South
702-733-3111; 888-308-8899
Who knew one of the oldest and least elaborate casino-resorts on the Strip would have a backyard so big, so lush, and so much fun? The network of water slides would have been enough, but there is also a second pool with a pounding 14-foot waterfall, and a third, more conventional and sedate pool, for those seeking a calmer atmosphere. Even that last one is clever, with 10-foot-tall concrete pink flamingos quietly spitting water out of their beaks. Live flamingos and African penguins are in the nearby garden.
Jamie: ''We'll be back. Awesome."
Swimmable: 10.
Coke $2.25, rum and Coke $5.50.
Mandalay Bay Resort & Casino: A+
3950 Las Vegas Blvd. South
877-632-7800; 702-632-7777
As we treaded water in the 7-foot-deep pool waiting for the waves to start and sweep us to the sandy beach, we wondered: Why didn't anybody think of this before the Mandalay opened in 1999? There are three more conventional pools and a lazy river. (An adults-only topless pool is positioned such that youngsters cannot see it.) Lifeguards seem happy, vigilant, and alert, rare on the Strip.
Jamie: ''Just three more waves, OK? Please?"
Swimmable: 10.
Pepsi $2.75, rum and Pepsi $5.50.
The Palms Casino Resort: A
4321 West Flamingo Road
866-942-7777; 702-942-7777
The Palms offers the most intriguing and diverse options. There are lounge chairs, hammocks, tables, and seats built into the shallow end of the pool; purple mattresses on a sandy beach; and canvas canopies. A 3 1/2-foot-deep above-ground glass pool has windows in the side for taking pictures of friends underwater. Rent backgammon sets or shoot a round of pool on the deck.
Jamie: ''Very cool. Add a waterfall somewhere and this would be an A+."
Swimmable: 10.
Coke $2.50, rum and Coke $6.50.
Bellagio: A-
3600 Las Vegas Blvd. South
888-987-6667; 702-693-7111
Elegance is the calling card of the
An extra perk: free water aerobics classes at noon for guests. The water, though, had a strangely unpleasant, salty taste found at one or two other pools in our survey.
Jamie: ''Pretty, but the hot tubs aren't very warm or bubbly."
Swimmable: 7.
Coke $4, rum and Coke $6.50.
The Mirage: A-
3400 Las Vegas Blvd. South
702-791-7111; 800-627-6667
The first of the new generation of themed resorts plays up its Polynesian aesthetic with aplomb. The main pool winds across a 65,000-square-foot expanse with six waterfalls rolling off a grotto. A smaller, calmer family pool has three slides.
Jamie: ''Cool slides. Slides are important."
Swimmable: 9.
Coke $3, rum and Coke $5.
MGM Grand: A-
3799 Las Vegas Blvd. South
877-880-0880; 702-891-7777
The city's most gargantuan hotel had to have a big water feature if only to accommodate its capacity of 10,000 guests. It has five pools sporting show-biz names like Talent Pool, and a lengthy, lazy river takes almost 10 minutes to float around. It was, however, oppressively crowded and noisy.
Jamie: ''The lazy river just goes on and on. This rocks."
Swimmable: 8.5.
Coke $3, rum and Coke $4.75.
Four Seasons: B+
3960 Las Vegas Blvd. South
702-632-5000; 877-632-5000
The first thing we saw were pool attendants spraying cans of mist on women relaxing in lounge chairs around a worm-shaped pool. This hangout for the ultra-rich will not appeal to children, but it's not supposed to. It's intended to be a relaxing respite for wealthy travelers, and it does that well, considering that it borders Mandalay Bay's frenetic beach.
Jamie: ''Boring, but the water was nice."
Swimmable: 5.
Coke $4, rum and Coke $7.50.
Rio All Suite Hotel & Casino: B+
3700 West Flamingo Road
800-752-9746; 702-777-7777
Four pools span a huge area, each with distinctive features. One is shaped like a clam and has a large concrete shell in the middle with a giant pearl that spews water. Another is shaped like a fish, with orange and black tiling on its floor. The third has a Jacuzzi tucked behind a waterfall. The fourth has a sandy beach that leads to a deeper area accented by a striking waterfall. The beach was an interesting try, but the sand is coarse, uncomfortable to walk on, and makes the pool dirty. The 5-foot deep end is deeper than standard. A blackjack table is under a canopy in the center.
Jamie: ''They need softer sand in the beach-pool thing, but that hot tub behind the waterfall was pretty cool."
Swimmable: 9.
Coke $3,rum and Coke $6.
Tropicana Resort and Casino: B+
3801 Las Vegas Blvd., South
702-739-2222; 888-826-8767
This dinosaur may be one of the Strip's least-noticed resorts, but to our surprise, the place had a large pool with curves and caverns topped off by a fountain cascading dramatically from 15 feet above. There's a bar in the pool with swim-up blackjack tables. Palms and other trees fit the jungle theme. The downside is lots of tree bits in the water, especially in the hot tub. A plus: The pool is more than 6 feet deep in parts.
Jamie: ''That waterfall just pounds you!"
Swimmable: 10.
Coke $2.50, rum and Coke $4.50.
Caesars Palace: B
3570 Las Vegas Blvd. South
877-427-7243; 702-731-7110
Lifeguards at the Luxor and MGM Grand said Caesars' was their favorite pool on the Strip. We could only figure they liked the prospect of glimpsing topless women. This is one of the few Strip hotels that allows what they call ''European-style topless sunbathing" at the Venus pool (blocked from children's view). The central pool, with a soaring rotunda in its center and fountains shooting water 15 feet high, is a sight to behold and frolic in. Still, that's all there was. The water was uncomfortably cold, and the deck is made of some material that gets so hot that walking barefoot is almost dangerous.
Jamie: ''It's nice, but not really that great."
Swimmable: 6.
Coke $2.50, rum and Coke $5.50.
Luxor: B-
3900 Las Vegas Blvd. South
702-262-4000, 800-288-1000
Four pools at the base of the pyramid, one of which has 20-foot Egyptian pillars topped by busts of goats that spit water from their mouths. The other three pools surround a structure that should have been a waterfall that spills out into each, but it was in disrepair. One lifeguard dozed; another wasn't even wearing a swimsuit.
Jamie: ''Is that bird poop on the broken waterfall?"
Swimmable: 6.
Coke $2.50, rum and Coke $4.50.
Paris: B-
3655 Las Vegas Blvd. South
702-946-7000; 888-266-5687
This underwhelming and ordinary spread on a third-floor deck is nevertheless fun because of the scenery. A leg of the ''Eiffel Tower" juts into the side of the plaza, and visitors can walk beneath it after a dunk in the star-shaped pool to grab a bite from the snack bar. An open-air cafe is on the plaza.
Jamie: ''Cool scenery, cold water."
Swimmable: 5.
Coke $2.50, rum and Coke $4.50.
Wynn Las Vegas: B-
3131 Las Vegas Blvd. South
888-320-9966; 702-770-7100
The city's newest, and most expensive, resort has received early complaints about the pool, but we thought it wasn't that bad. It's a long narrow stretch of water that starts out quiet on one end and goes all bombastic on the other with swim-up blackjack and loud music. It's harder to relax here than it should be for such an elegant hotel, and the area for children is small.
Jamie: ''How many billions did they spend on this?"
Swimmable: 6.
Coke $4.50, rum and Coke $7.
TI Treasure Island: C
3300 Las Vegas Blvd. South
800-288-7206; 702-894-7111
Recently rechristened the ''TI," the hotel has adopted a more adult focus, and as part of that process, this small pool lost its slide. Now, it's just an average Vegas puddle, refreshing but not enthralling. One good thing: The lifeguards are a bit bossy, a welcome change.
Jamie: ''Umm, what happened to the slide?"
Swimmable: 5.
Coke $2.50, rum and Coke $4.50.
Excalibur: C
3850 Las Vegas Blvd. South
702-597-7777; 800-937-7777
For a resort that prides itself on being kid-friendly, it's peculiar that the only interesting water feature -- a small waterfall -- is accompanied by a do-not-touch sign. The mushroom-shaped pool is surrounded by some theme-appropriate and cute castle facades, but the water was too cold.
Jamie: ''Why can't we touch the waterfall?"
Swimmable: 5.
Coke $3, rum and Coke $4.50.
Harrah's Las Vegas: C
3475 Las Vegas Blvd. South
702-369-5000
With the building's motel-like facade towering over it and no view of the Strip, you could just as well be at a Days Inn in Boise, Idaho. One oddity was that the walls and floor of the pool are made of metal: Bounce on the floor and you'll feel vibrations. Two nice features include a chair massage for $20 for 15 minutes, and misters that distributed cool puffs of moisture on nearby loungers.
Jamie: ''I liked the paintings of the parrots, but why are they there?"
Swimmable 7.
Coke $2.50, rum and Coke $5.
Stratosphere: C-
2000 Las Vegas Blvd. South
702-380-7777; 800-998-6937
As with everything else at this hotel, the view's the thing. In this case, it's not much. From the eighth-floor deck you look at the smog-shrouded mountains to the west or the Sahara's neon billboard to the south. The pool is adequate, although it had the worst-tasting water.
Jamie: ''Just imagine if the pool were at the top of the tower!"
Swimmable: 4.
Coke $3, rum and Coke $3.50.
Aladdin Resort & Casino: D
3667 Las Vegas Blvd. South
877-333-9474; 702-785-5555
You know you're in trouble when you get off the elevator on the sixth floor and walk out to the pool area only to have your sidekick ask, ''Where's the pool?" The dominant element here is a concrete plain with lounge chairs and tables and two small, unremarkable pools on raised landings. I could put a lounge chair on my driveway for the same effect.
Jamie: ''This is stupid."
Swimmable: 2.
Coke $2.50, rum and Coke $5.
New York New York Hotel& Casino: D
3790 Las Vegas Blvd. South
702-740-6969; 800-693-6763
Whoever decided to place this skimpy pool directly below the peak of the roller coaster must be fired. Imagine spending $200 a night to sit poolside and listen to the thunderous racket of the cars rising to their crescendo followed by the charming screams of riders as they plummet -- every few minutes. The view, too, of the parking garage and a sign for Interstate 15, is miserable.
Jamie: ''Boring, but the hot tub was hot and bubbly."
Swimmable: 2.
Coke $3.50, rum and Coke $5.50.
Venetian: F
3355 Las Vegas Blvd. South
702-414-1000; 888-283-6423
You would think that a resort based on a city of canals would offer a second-to-none water feature. You would be so wrong. This $1.5 billion casino, which in other ways is sensational (elaborate paintings, enormous and elegant suites, and gondola rides) offers a pool area that is downright hideous: three ordinary rectangles in a big shadeless stretch.
Jamie: ''Do we have to actually go in?"
Swimmable: 2.
Coke $2.50, rum and Coke $6.50.
Steve Friess is a Vegas-based freelance writer and cohost with Miles Smith of the weekly Internet radio show and podcast, ''Vegas S&M," at www.lvrocks.com/sm.html. 
