LYNN – Attention Massachusetts boaters: Don’t crack that Heineken in view of a Coast Guard cutter over the weekend.The Coasties are keeping a sharp lookout during the July 4 holiday for boaters quenching their thirst while at the helm as part of a federal crackdown called Operation Dry Water.According to the Coast Guard, 21 percent of recreational boating accidents in 2007 resulted from drinking. Those statistics, released in June, prompted the Coast Guard to team up with local law enforcement agencies to raise awareness of the dangers of boating while drinking alcohol or taking drugs.Al Johnson of Lynn, the Coast Guard’s boating safety expert at the First District headquarters in Boston, said the goal is to get impaired boaters off the water and make them savvy to legal consequences and the potentially fatal effects of boating under the influence – aka, BUI.The National Transportation Safety Board affirmed that recreational boating accidents are second only to highway mishaps in the number of transportation fatalities.What the safety analysis didn’t emphasize is that most fatal boating accidents linked to alcohol or drugs don’t involve sailboats. Such cases typically center on a high-powered craft steered by an inebriated skipper cranking at top speed on a lake or along the coast.Participating agencies have been asked to step up enforcement of BUI laws by increasing patrols and conducting drunken boating checkpoints, Johnson said. A Coast Guard advisory noted that since 1998, 39 recreational boaters and paddlers have died over the Fourth of July holiday weekend in the First District – which stretches from Newfoundland to Pennsylvania. Eighteen of those deaths were alcohol-related.