NPS allows about 2 dozen outfitters to rent you kayaks or canoes for guided or self-guided tours down Black Canyon south of Lake Mead (see NPS website for more info). Permits and boat costs differ by vender.

Do a 2-3 day from Hoover Dam to Willow Beach or longer to Placer Cove.

Arizona Hotsprings (about a mile down the river) is a popular place to camp on this river route, but I'd check out Moonscape first! There was a big-ish group right off the river where there is a clearing big enough for 10 and we hiked about a half mile past them toward Moonscape Hotsprings where there is another clear campsite with a fire-ring to the left. Totally secluded & closer to the hot springs!

River levels change a LOT so make sure to tie your boats down to something before exploring any canyons / hot springs.

You *can* get to this site without a boat but only with some solid nav and rappelling skills and gear. We saw a small group who had rapped in with tiny inflatable boats and floated out. Very cool, also looked exhausting.

BYO everything - including firewood - and pack EVERYTHING out (including poop and no ground fires allowed, so bring a big wok or baking pan).