Although my current boat is equipped with an installed AC system, I faced a dilemma when I had to put my boat in the yard for two weeks in steamy August: You can't use the system when the boat is out of the water! (my marina wouldn't allow running freshwater hose overnight)

 I had a small 5K BTU window unit sitting  at home  So I cut up an old plastic yard sign, added some duct tape and a tarp to keep rain out, and put a 1x4 board over the hatch of my aft cabin where I sleep. Ugly, but worked well enough!!

3 years ago I visited a friend who had just bought a used 30' boat.  I advised her to look for a used "carry-on" AC unit (they are no longer being sold).  Turns out they are almost impossible to find and darned pricey if you do. Recently saw one on eBay for $550 after shipping. 

I still had that same 5000 BTU window unit from my haulout .  I told her I'd give it to her and make her a "cleaned up" AC adaptor that was nicer than the one I used for my boatyard episode.

The thinking that went into making something she'd be able to easily deal with resulted in a CoolBoat prototype.

  
After almost 3 years of tweaks, the"CoolBoat®" AC adaptor is now patent-pending and available to anyone who wants a good night's sleep on a cool boat.