Hi there,
My boyfriend and I are planning a similar trip to Belize, and I have just read DocVikingos replies. We'll be diving for 2 days after we arrive, and take the 3rd day to lgo hiking and take a break before our flight. You can definitely dive after landing. That is not the problem. the problem lies with flying after diving. If by any chance you have an airbubble in your body after diving, it might just clear by itsself, and you wont notice it. if you fly however, you only increase the danger of something happening. Here's an abstract from a medical site. I have many friends who dive all over the world, and we have all always waited 24 hours before flying. Why risk it? To describe this as conservative is really dangerous I think. You only need to have a problem once.
Here's the exert:
What are the dangers of SCUBA diving & airplane travel?
SCUBA diving exposes your lungs to a high pressure environment, whereas airplane travel is a low pressure environment. Your lungs undergo a dramatic change in pressure when going between these two extremes. The bigger the change in pressure the greater the risk for arterial gas embolism. The best thing you can do to avoid this is to leave at least a 24 hour period between your last dive and the time you board the airplane for your flight home.
Many avid divers who want to maximize their dive time are tempted to schedule their flight home in the evening, to get in one last morning dive -- you should avoid this! Your last day in the islands should be spent re-acclimating to sea level pressures.
This will also give you and your companions time to observe you for the symptoms of arterial gas embolism. If you manifest any symptoms, such as lightheadedness, dizziness, mental confusion, numbness or tingling or sensory disturbances of any kind, you should be brought to a re-compression chamber. Under these circumstances, the last thing you need is to be up in a plane.
So take it easy on you last day in the islands, and avoid the temptation of diving on the day of your airplane departure.