It depends in part on your tolerance for digging around at various bureaucracies looking for the hoops you're gonna have to jump through. It isn't that a normal humanoid type cannot do it, but it tends to be frustrating and boring and unpleasant; hence the advice to have an agent do it. But the deal is, if the agent can do it, so can you; however, the agent has local knowledge and you may or may not. So there you go. Yes, it's doable, the difficulty is dependent on you, the situation of the boat you want (can you buy direct from the owner and only have to deal with registration
issues?), and so on.
We bought a boat in a foreign country and all went smoothly. We bought from a private owner, no loans were involved, and it went really well. YMMV A whole lot has to do with how well you know boats in general and what you want. If you're a good judge of a boat and of a seller, you'll most likely do well. Like I said, YMMV.