About this time of the year, you probably start thinking about water more than ever. It's hot, you're dry, and your body wants hydration. But drinking water's not as simple as it used to be.

Twenty years ago, water was something you got by turning on the spigot and sticking a glass under the faucet. Then, in the mid-'70s, bottled water pioneer Perrier introduced its single-serving sparkling water to the United States, and we were hooked-so much so, that in 2006, Americans drank $15 billion worth of bottled water. Pricey, designer H2O from such far-flung locales as Fiji and New Zealand share shelf space alongside dozens of other varieties, some from underground springs or with natural minerals, some with added vitamins or fruit essences. And some go for upwards of $2 a serving.

How to choose? If you're passionate about bottled waters, check out

Fine Waters: A Connoisseur's Guide to the World's Most Distinctive Bottled Water, by Michael Mascha. Some to try, with highlights of each:

Still water. Nearly 40 percent of bottled water sold in the United States is nothing more than filtered and purified tap water.

PENTA: Ultrapurified, said to hydrate the body more efficiently and increase antioxidant activity.

ESSENTIA: Treated with ionic separation; very high pH of 9.5.

MOUNTAIN VALLEY: Packaged in green glass bottles; domestic source, from forestland in Hot Springs, Ark.

ETERNAL: Artesian water from New Zealand; alkaline pH of 8.0 and naturally occurring electrolytes.

FIJI: From an artesian aquifer near a rainforest in Fiji; high in silica.

METROMINT: Purified using reverse osmosis; mint essence added for fresh taste.

Sparkling water, seltzer, and carbonated water were first used by ancient Romans for their healing benefits; they became popular in the late 1700s, when chemists discovered how to add carbon dioxide to still water to replicate the bubbly beverage. Sparkling mineral waters are generally naturally carbonated, often from volcanic activity that infuses the water with carbon dioxide. Naturally effervescent water is also mineral rich.

GEROLSTEINER: From Germany's Eifel mountains; rich in minerals; available in glass and plastic bottles.

SAN PELLIGRINO: From San Pellegrino Terme, in the Province of Bergamo, Lombardy, Italy; naturally effervescent and rich in minerals.

PERRIER: From the city of Vergèze in the south of France; available in glass or plastic bottles; flavored varieties are also available.

Enhanced water. These are waters that have added flavors or vitamins, and may provide some kind of function or purpose.

KNUDSEN SPARKLING ESSENCE: Contains organic lemon, mint, blueberry, or cucumber essence; no calories or sugar.

GLACEAU VITAMIN WATER ZERO: Calorie-free; flavored with fruit; sweetened with Truvia; contains added vitamins and minerals.

VOLVIC FLAVORS: Made with Volvic Natural Spring Water; orange and lemon flavors added; no sweeteners or calories.

HINT WATER: Unsweetened and calorie-free; infused with fruit flavors.