Sadly, lots of sailing disasters have occurred when the boat owner experienced a problem and others on the boat didn't know what to do. A situation can occur at any time: you reach for your hat that the wind has blown off and tumble overboard, and the other person on board - a spouse, a friend, a new crew - is unable to get the boat back to you in time. Or a sudden wind shift causes an unexpected gybe at an inopportune moment when you are standing to reach for a loose sheet, and the swinging boom knocks you unconscious or overboard. There are hundreds of ways to end up in the water, and many of us are more relaxed about safety concerns when someone else is on board then when we are sailing alone. But if the other is not well versed in sailing techniques or doesn't know how to start the engine or call for help, you might as well be alone. In recent years, several sailors have died in the simple situation of taking a quick swim to cool off and the boat drifted away faster than they could swim back to it - while someone on the boat watched helplessly. But it doesn't take much effort to make sure your sailing partner knows what to do in case of an emergency. Here's a checklist of essentials to teach that person when you head out.