If you are worried about evacuation costs, PADI dive insurance is a good deal. You don't have to be a diver:
http://www.padi.com/blog/2014/05/02/dan-scuba-diving-insurance/(Obviously, you should check that it covers whatever situations you are anticipating.)
Anecdotally, I heard they keep a plane in Miami with a compression chamber that they use to evacuate anyone needing in it in the Caribbean.
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