Start with your available time
A day cruise can fit a shorter visit, while an overnight itinerary gives more time away from the road transfer. Compare actual time on the water rather than the headline length of the excursion.
Read the whole itinerary
Check the departure harbour, transfer arrangements, route, stops and meal inclusions. If kayaking or a cave visit matters to you, verify that it is included and what happens if conditions change.
Choose comfort with care
For an overnight trip, compare cabin layout, bedding, meals and accessibility. Share dietary or mobility needs before booking and ask the operator what can be accommodated.
Keep weather flexibility
Sailings and water activities depend on local conditions and official instructions. Review the cancellation and rescheduling policy, and leave some space around your trip rather than booking a tight onward connection.
Destination background: Vietnam National Authority of Tourism. Routes, schedules, conditions and booking terms should be checked with the provider. Some images are illustrative.