I planing to go for a diving since I am already in VIetnam , I will be dropping by Hoi An , Dalat , Nha trang , Hanoi , Saigon , Hue , Mui ne . Can I know any of this places I can do diving ?
You can also dive at the Cham Islands offshore from Hoi An although most people seem to snorkel there.
I know that there is some diving in the Nha Trang region, boat trips to outer islands are the serious divers choice (maybe you can encounter a chinese patrol boat!). Other wise, Phu Quoc is the spot, but it's a long haul.
Check out this topic: Fishing or scuba diving tour in Nha Trang and Beautiful beaches in Vietnam