Many traveling Undercurrent subscribers undertake additional
tours before or after a dive trip. In today's post 9/11 world,
valid passports and visas are a must for travel. I learned that
before a planned stopover in Hanoi on my return trip from
Thailand. As I prepared to board a flight for Hanoi in Phuket,
the ticket agent handed back my passport. "Where is your
Vietnam visa? You can't fly to Hanoi without one."
I was startled. I'd put my faith in my travel agent to handle
  the travel requirements or at least inform me of my responsibility,
  and I was stuck. I was sent to Bangkok where Vietnam Airlines
  determined that I could get a visa at the Hanoi airport, so I plodded
  on to Hanoi, only to learn it wasn't true. I was detained for
  22 hours in a shabby airport "transit" room, and when the
  efforts of my Hanoi tour agency failed to get me a visa -- they
  simply didn't have enough time to work through the bureaucracy
  -- I was escorted directly to a flight to Singapore. 
My U.S. travel agent said he had no responsibility because
  he didn't book my land travel in Vietnam -- though he did
  book the flights. He whined that he barely made five percent on
  my fare. So what!  
Yes, as a savvy traveler, I should have known to get a visa. So I
  want to suggest that you personally check all official travel
  requirements. There's hardly a country today that doesn't
  require a passport and more and more are requiring visas, if for
  no other reason than as retribution to U.S. citizens for new U.S.
  immigration rules. Today, "proof of U.S. citizenship" means a
  passport, not a birth certificate. Having your passport or visa
  expire while you're in another country can mean detention.
  And, if your passport isn't valid six months beyond your departure
  date, you may not be allowed to leave home in the first
  place.  
NEED A PASSPORT OR VISA IN 48 HOURS, OR A WEEK? Travel
  Document Systems makes it easy with their online registration.
  Find them at www.traveldocs.com to fill out a form online or call
  their Washington, D.C., office at 800-874-5100 or 202-638-3800,
  or the San Francisco office at 888-874-5100 or 415-773-2829. You
  pay according to how quickly you need it, and they can handle
  requests in a couple of days.