Oh, man, in my 20s I got really into the idea of boat camping. Lots of Phil Bolger designs, obsessively reading the Duckworks forums like I do Saddlehunter today. I lived in an apartment and was gearing up to move to the desert; my boat was about halfway-built by the time I had to move and my dad didn't have space for it, so he had to saw it apart to fit it in the garbage truck. Anyway... you can probably find a Walmart dome tent with a footprint about the size of your boat. This guy sets it up inside the boat, check the 24-minute mark:
I've also seen people cut out the bottom of the tent and attach the poles to the gunwales of your boat, with netting or skirting to keep the bugs out, and a cot or air mattress across the thwarts.