Sailboats aren't a bad place to start. But you'd still need to find a source of fresh water, quickly. The ocean will keep you safe from most disasters, except malnutrition, dehydration and tsunamis.
Yeah you would def need to be prepared but it would get you away from danger so you could make a better plan with more specific circumstances. But then you might have to worry about zombie dolphins or sharks.. A boat can save your life in a Tsunami though...I mean if you are already far away from the coast when it happens, you should be ok.
I don't think the movie type of zombie apocalypse could happen, either. But, it is a fun critical thinking exercise, yeah?