There are have actually been a few young people sailing around the world solo in the last few decades[1]. I'm sure for each of those there are many who perform more mundane tasks or have jobs doing things like ferrying or tours. It's perhaps not as illustrious as it once was. Instead of captaining a ship we now have young people starting companies, trading one kind of venture for another.
1. http://www.mnn.com/lifestyle/eco-tourism/stories/5-teens-who...