Iv'e been having some idle thoughts about the same thing. There are the "marine" options that fit into the forward hatch, the standard small window home units that people adapt to hatches and companion ways and the "portable" ac units that can go inside, running the exhaust hose to the outside.
The last one has caught my attention. The main issue is finding a good reliable model. The reviews can vary a lot on the same model. The other issue is how they get rid of the evaporated water. Some only have a pan that needs to be emptied, others have a drain than can be run to the bilge / drain etc. Some brands say the moisture is taken care of through the exhaust (hot air duct to the outside) I question how well that works in a high humidity area.
The marine units look good but cost more. The window units are the cheapest but require more work to adapt them to a boat (and may look a bit less refined) The portable ones are hidden from the outside and can stay in place when sailing.