We just cruised Vietnam this past October. We were on Seven Seas Mariner which is larger than the Clipper ships.
Vietnam is a fantastic place to cruise. We went into Hong Gai for tours to Hanoi. Well worth seeing. We overnighted there and then sailed through Ha Long Bay. Next stop was Chan May, a deep water port between Da Nang and Hue. We arranged a private tour of Da Nang that was fantastic. Next stop was Saigon for two days. Quite interesting sailing up the Saigon River. Along with a tour of Saigon, we took a tour to Cu Chi Tunnels and Cao Dai Temple.
This was part of a longer cruise from Hong Kong to Singapore. This itinerary is repeated by a number of different cruise lines. One port that we didn't stop at in Vietnam that many enjoy is Nha Trang. This is a resort town.
Hope this helps.