I did a 2 day one night trip in Ha Long - actually found a company that would take me up to Bai Tu Long bay which is slightly north and has far less tourist boat traffic. Take off from the boat is worthy of its own thread, many lessons learned, but thankfully didn't crash. Basically Mavic gets very confused with a moving boat. Worked best (safest) to take off and land when the boat was stopped, from the stern, into the wind, away from cables, etc. I booked a private boat to be able to facilitate all this coordination with the captain and crew. You might not be allowed to launch from a shared boat - depends on the company.
Pack the props however makes you feel good, but your batteries need to be in your checked baggage - signage was serious about that. I had my propped mavic go through a ton of xrays through China and internal flights in Vietnam, and absolutely no question. My laptop and chargers received more attention.