Seltzer is losing its innocence. The bubbly water has emerged as the newest playground for booze marketers that are aiming to lure health-conscious drinkers with spiked versions.

The newest brand is White Claw Hard Seltzer by Mark Anthony Brands, which also owns the Mike's Hard line of flavored malt beverages. The seltzer, which is hitting stores now, comes in natural lime, black cherry and ruby grapefruit flavors and checks in at 110 calories per 12-ounce can. That puts it on par with the calorie count of the average light beer. But White Claw's alcohol by volume of 5% is a bit higher than mainstream light beers, which are usually about 4.2% ABV.

The launch follows the national debut in May of Truly Spiked & Sparkling by Sam Adams-maker Boston Beer Co. That brand checks in at 5% ABV and 100 calories for 12 ounces. Earlier this year, Wachusett Brewing of Massachusetts launched "Nauti Seltzer."

The veteran of the group is a brand called SpikedSeltzer, which launched in Connecticut in 2013 and as of last summer was in 10 states, according to an April report in Craft Business Daily. The brand is now in 14 states, Bermuda and the British Virgin Islands, according to a spokeswoman.

While hard seltzer is an emerging category, "it is still relatively untapped with only a small group of players in the space," Danny Brager, senior VP of Nielsen's Beverage Alcohol practice, said in an emailed statement. But "this category is certainly one to watch this summer."

The nation's two largest brewers, A-B InBev and MillerCoors, do not currently market spiked seltzers. But it's a pretty safe bet they will enter the category if seltzers gain traction. The two brewers recently introduced hard sodas after brands such as Not Your Father's Root Beer, which is distributed by Pabst Brewing Co., found success.

Seltzer is being positioned as a lighter alternative to heavier and more intensely flavored hard sodas. As they enter the market, Boston Beer and Mark Anthony are citing the rising popularity of regular carbonated bottled water as well as interest in lower calorie booze options. Sparkling water sales have grown 20% over the past year, according to Nielsen.

White Claw wants to lure drinkers of vodka and soda cocktails, which it says are the preferred choice of 27% of alcohol consumers. "White Claw really delivers on that idea of vodka and soda in a very convenient 12-ounce sleek can," said Sanjiv Gajiwala, the VP-marketing at White Claw who also oversees Mike's Hard. A six-pack of White Claw sells for a suggested price of $9.99.

The brand is taking a modest approach to marketing, with efforts focused on social media and sampling at stores, running races, golf courses and yacht clubs. White Claw does not have a creative agency, Mr. Gajiwala said. Mike Hard's agency is Trisect. Boston Beer's Truly brand will also focus on sampling, according to a statement from the company.

Mr. Brager stated that the hard seltzer category "has the most appeal to the female consumer set -- a trend that aligns with a larger industry shift towards beer and spirits beverage makers diversifying their offerings to cater to the palette and preferences of women."

White Claw's messaging will be gender neutral and focus on product attributes such as the use of natural juices and "why ours tastes better," Mr. Gajiwala said. The brand name is a reference to so-called white claw ocean waves that travel in sets of three. Packaging shows three waves against a white backdrop.

Unlike Mike's Hard and most hard sodas, White Claw is not considered a flavored malt beverage, Mr. Gajiwala said. The gluten-free drink is made by fermenting sugar, putting it through a seven-stage filtration process and adding sparkling water, natural flavor and juice, he said. While flavored malt beverage drinkers want intense flavors, seltzer drinkers are "a whole different consumer that is really looking for lighter flavors, natural ingredients and something that fits their active, healthy, on-the-go lifestyle," he said.

Still, alternative alcohol formats tend to face a boom-and-bust cycles. For instance, a couple years ago hard ciders were the rage with growth luring new brands from MillerCoors and A-B InBev. But the category has fallen on hard times of late. As of May 28, cider sales were down 14% year-to-date, according to Nielsen figures cited by Beer Marketer's Insights.