Just kidding. On our old boat which we lived aboard for 6 years and cruised on, we lived without a/c or hot water... and I did my full pregnancy on that boat in the muggy Chesapeake Bay. I joke that I was so flush with pregnancy hormones I didn 't notice the heat.
We have 2 air conditioning units dockside now with a little one on board. But I still can feel a BIG difference when I shade out the hatches. I buy scrap fabric at the fabric store (about a $1 for a fat quarter) and then pop it between the screen and the hatch. You still get some light (in lovely colors and prints) but it keep the radiant heat WAY down.