Today's pools aren't all the energy guzzlers or chemical soups of the past -- like cars, new technologies have created efficient systems to treat and clean the pool, as well as light and heat it.

And the desire for a personalized outdoor living space has some people bringing home more than snapshots from their vacations. T.J. Moreland of Merlin Industries, a pool product supplier in Hamilton, N.J., notes that homeowners often want to incorporate elements they've seen from hotels or water parks -- submerged bar stools, liners patterned like aquariums, or even depictions of favorite activities.

''We made a liner look like a baseball field, complete with infield, bases, and home run distances on the pool walls.''

Here are some updates for America's more than 5 million in-ground pools, with nearly as many above-ground pools, according to figures from the Association of Pool and Spa Professionals:

Salt does a good job of keeping water clean and preventing algae, and costs considerably less than standard chlorine treatments. Ultra violet light also breaks down harmful materials, and bromine is touted as a less harsh chemical additive. Ozonators, which have been widely used in European pools for years, are finding favor in North America now as an alternative for those sensitive to chemicals. Ozone is an effective remover of sunscreen and body oil, and also destroys cryptosporidium, which can cause intestinal upset.

Solar heating systems help reduce heating costs, although their effectiveness depends on the pool's location. Hammacher Schlemmer's floating solar heating rings can raise the water temperature 3-4 degrees in a week when covering 70 percent of the water's surface.

Wet decks are another new trend; basically wide, submerged steps, wet decks make it easy for young children, seniors, and even pets to safely enjoy the pool without swimming. They're popular as gathering spots as well, and can be built with umbrella housings and non-slip surfaces.

Modern shapes

Naturalistic, freeform pools have been popular in recent years, but Joe Vassallo of Paragon Pools in Las Vegas says another trend among his clientele is pool aesthetics.

''They are leaning toward a more contemporary casual style; more geometric than lagoon, and incorporating materials like travertine and flagstone. Glass tiles are re-emerging with more colors, and mosaics and pavers are replacing concrete decking.''

A pool bottom designed to look like a ballpark may be unusual, but industry experts say more consumers are turning to liners decorated with sea creatures or some version of a Roman bath -- whether it is on a printed vinyl liner, or crafted of mosaic tiles directly onto the bottom and sides of the pool. Bob Rogers of Ceramic Pool Art, an online retailer, says new frost-proof mosaics are a boon for pool owners in cooler climates. ''Designs are becoming more sophisticated,'' Rogers says. ''Mosaics are now being used on pool decks and stools, too.''