It smells sweet and looks innocent. But don't be fooled. Smoking fruity tobacco through a colorful water pipe called a hookah is a growing alternative to cigarettes among young people. Hookah bars have sprung up across Long Island, including one recently approved to open in downtown Farmingdale aimed at young adults. But studies have shown that hookah users are exposed to harmful chemicals, including carbon monoxide and carcinogens, just as cigarette smokers are. Hookah's hype may come from dangerous myths, including the incorrect belief that water can filter out toxic compounds. Gov. Andrew M. Cuomo's decision Friday to sign a bill to ban the sale of hookah paraphernalia to minors underlines the practice's dangers and may deter youngsters from picking up the habit. Not getting hooked on hookah is the one and only safe alternative.