We went in right before dark, but yes, they would try to come down on us, or avoid us. We could cover a lot of river, though, with three two-boat patrols, spaced well.
Why did you not move at night
They could easily hear us coming at night, and get a squad-sized unit down on the riverbank with a few RPGs and RPDs. Not that big a problem on the big rivers, but the ones I worked were, in some places, only about three times as wide as the boats (or less), and -- while we were usually shooting back within a second and a half -- it was hard for them to miss at those ranges. If we moved, we got zapped.
We usually got all the CAS we needed, day or night. Sometimes it took half an hour or more to get there, and some kinds were much more effective than others. If we were in trouble, though -- a boat dead in the water and taking fire, for instance -- someone would always "pull out all the stops" and come to our rescue, sometimes taking unbelievable chances.
Our guys are like that...