The water remains very cold year round, since it is released from the base of the Glen Canyon dam, slightly warmer that far down river, but very cold still. I have been on trips where people have rented gear from Ceiba, and it was fine. You have a few options for gear rental and shuttle, you could even pay to have a company shop for the trip if you want, pick you up at Pearce, make ya lunch, and drive you to the airport, I believe.
You may prefer to spend more of your time above QuarterMaster canyon, as the Hualapi run Heli tours down to there landing pad at QuarterMaster Canyon, it is pretty constant, I can't believe how many choppers they have down there.
March does have a reputation for being windy up river that time of year, so heads up.
Though small, I really like camping at Seperation Canyon, Surprise Canyon looked really good last month to, camps get scarce after that. The stop at Columbine Falls is really nice right now, and following the trail along the cliffs on the left from the rocks, is the best access. The beach there looks like a nice small camp right now, but should check with the Park Service beforehand, as camping within 300 yards of the falls is not permitted. The beach looks farther away from the falls than that to me, but I don't know what thear tape measure says.
It's still an enjoyable trip down there in my opinion, despite the choppers and silt banks bellow Gneiss.
Have a great trip!
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