I suppose that depends on how you define the word "effective". The problem with word of mouth is that first, you don't meet a lot of mouths when you need them. And second, of course, you can't be sure of the quality of the information unless you know the source.
So 'effective' ? Sure, if it comes from your small circle of friends in a timely manner. But totally ineffective from the boatyards point of view, they're not reaching many new customers that way unless they are willing to wait a few years.
Good (and possibly the best) LONG-TERM marketing
, but that's not necessarily effective marketing if you need business this year or next year.