Recess-I know you want to tackle the water maker. So this project would be a piece of cake compared to that.
Take a window unit (walmart style like what's in your pic).
Cut the condernser out and remove the cooling fan for the condenser and replace it with a tube in tube heat exchanger. They cost around $100 for the cupronickle type that you would need.
I would take it to a AC repair shop and have them solder it in the AC unit and charge it.
You would have to have an available through hull to feed it sea water, but that would give you true marine AC, with a remote control.
I bet you could get a shop to solder and charge that for $100, but I am not sure.
If anyone sees a problem with this please let me know. I have already tore apart a small wondow unit, but I haven't bought the tube in tube yet. There is a place in Waco Tx that sells them. If anyone really wants to know I will dig it up.