I just got out of the beach water but I only go to the beach after 7:30 PM... when there are almost no sun rays. The water itself is very nice and soothing, but the intense sun glaring off it is VERY HARSH and draining for me. The tropical (Caribbean) sun is much more intense than even the hottest NYC sun.
From what you just posted, you do not sound like you are in shape to go to the tropical sun or air travel, etc. I can't make that call for you.... but I am finding that the process of travel, packing, airports, etc... even for a trip that is not adventurous or strenuous, causes a moderate amount of stress no matter what.
Hope you feel better and out of crashland soon.
I am pulling out, my energy is coming back slowly, sleep improving... hope you feel the same soon.