The best time of the year to do cruising in Vietnam personally is during winter especially for American or European people like me who are getting old and hate the cold. I have been coming in and out of Vietnam not only to get away from the cold but because I love nature. Vietnam has wonderful places to go that is just wonderful. They have clean and beautiful beaches, clean rivers and the people are just warm and sincere. But before embarking on this journey, I suggest you do first some research on where you want to go to and what you may want to see.