It’s that time of the year again, when the summer heat makes such water sports as swimming, snorkeling, boating, and water skiing almost irresistible.

One water industry tracker, analyst Larry Edelson, sees the enticement of H2O in a different light: As an explosive growth business that presently offers investors a shot at a couple of double-your-money stock ideas over the next 12 to 24 months.

“Water, water everywhere, but not a drop to drink,” British poet Samuel Taylor Coleridge wrote in 1798 — Mr. Edelson figures the poet caught early sight of a major global risk: a burgeoning worldwide water crisis that is now a reality.

In America, he points out, people take H2O for granted as a natural resource, not realizing how precious it really is and oblivious to the fact 20% of the world’s population, or about 1.1 billion people, do not have access to drinkable water.

Put another way, he says, only 1% of the world’s water is drinkable. In China, an estimated 500 million people have no access to clean water. In India, the crisis is worse, with more than half its cities suffering from a shortage of potable water.

The danger is present even in America. For example, a federal study has determined that because of harmful levels of sulfuric dioxide in the air, more than half of the 2,800 lakes in New York’s Adirondacks will be too acidic to support life by the year 2040.

The study also concluded that the San Gabriel Mountains near Los Angeles are already saturated with nitrogen — meaning that their excess nitrogen is seeping into the surrounding waters. In the Midwest, the report notes, there has been a drought going on for the past five years.

Mr. Edelson, who has tracked the water industry over the past three years for Weiss Research of Jupiter, Fla., underscores the severity of the problem by noting that every 45 seconds of every hour of every day a child somewhere in the world dies from the lack of potable drinking water. What’s more, a few years ago, a United Nations forum warned that by the year 2050, more than 2 billion people will die each year from diseases attributed to the use of contaminated water.

Out of crisis is often borne opportunity and, in the investment arena, that’s what has evolved out of the worsening shortage of drinkable water, Mr. Edelson said.

At present, water is about a $215 billion annual business globally, with about $115 billion being spent on water solutions, from pollution control to water desalination, and the remaining $100 billion on the sales of bottled water.

Given that more than 1 billion people currently lack access to potable water, it’s easy to understand how spending on water solutions could easily double or triple over the next decade or even sooner, Mr. Edelson said. Water, he tells me, is more expensive than oil: Mineral water costs about $10 a gallon — which is about six times more expensive than oil, which goes for $1.61 a gallon.

All told, there are only about a dozen companies working on energy solutions worldwide. The analyst rates two as potential doubles over the next one to two years. One is Calgon Carbon ($11.98), a premier manufacturer of carbon filtration systems with 2006 sales of $316 million. The other is Watts Water Technologies ($39.24), a maker of valves used in plumbing, heating, and water control applications.

Mr. Edelson said he expects Watts Water, which has a presence in China, to expand into ocean desalination, the conversion of ocean water into drinkable water. The company’s 2006 sales were $1.2 billion.

An exchange-traded fund in the water industry, PowerShares Global ETF Trust ($25.45), is another favorite, he said.

Mr. Edelson also views a water industry investment as socially conscious investing, an opportunity for people to help the world solve a major and critical problem.

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HOT WALL STREET RUMOR No, it’s not about some stock that’s supposed to double or triple, but rather growing buzz on the Street that Mayor Bloomberg, who has consistently denied any interest in the presidential race, is prepared to spend $1 billion in a run for the White House. Apparently, the overseas betting parlors don’t believe it. They rate the mayor as a real long shot, quoting his chances of winning the presidency at 50–1 to 70–1. (In other words, you put up a buck to win between $50 and $70.)

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