You are looking at the Colorado River which has just come from Lake Powell and through the Glen Canyon Dam. Many people boat on this section of the river with motor boats, rafts and kayaks. If you look closely at this photo, you can see the blue river rafts lined up below and to the right of the dam.
For rafters to get to these rafts, they have to be transported from the surface and down through a 2 mile long tunnel to the water's edge.
Horseshoe Bend is the half way point between the put in at the dam and the take out at the very historical Lees Ferry area. Most kayakers camp for one night near a beach at the base of the bend. Sounds like a very delightful way to spend a few days!