It is against the law to operate a boat, or be towed behind or alongside a boat with a blood alcohol concentration of 0.08 percent or more. Designating a driver is not enough on vessels. The concept works well in cars, but drunken passengers on boats can easily fall overboard, swim near the propeller, or cause loading problems by leaning over the side or standing up in small vessels, causing them to capsize. Everyone who drinks alcohol on board a boat is at risk. If you do drink, wear a life jacket.