Gorgeous area. We lived down in Saigon for a year and have traveled there numerous times. Everyone takes the
charter boats. Trying to take a personal yacht into VN is difficult and expensive (thousands of dollars to clear in). In the past you would have been required to have a VN nationale onboard at all times.
Don't know what the rules are now, but personally I wouldn't try to bring my personal
boat into the country. It's so incredible inexpensive to travel there via the well-developed tourist infrastructure, and the inland areas are incredibly interesting to see.
Perhaps reach out to your nearest consultate/embassy and ask around. Also check out Noonsite for more recent info. Let us know what you find.
BTW, the
water is green and murky and my whole
family came out of the
water in popular lagoons covered in
bilge oil. I suppose if you get away from the tourists then the water could be clean enough to run your
watermaker.