I think of fish moving up and down in the water column as deeper, mostly suspended fish. Most of the fish are shallow right now, so they're already in the upper column of the water. I find that rising water causes the fish to follow the rise into newly flooded vegetation, cover and structure. So I'd say they stay in the upper part of the water column but expand their range. That new water causes algae to form on all the vegetation within about 4 days. Phytoplankton and Zooplankton feed on algae. Small baitfish feed on plankton. Bigger fish feed on baitfish.
"Things turn out best for those who make the best of the way things turn out" - Zachary Troy Schrah - a young man with vision far beyond his years.