It’s a puzzle. If I had to pick one variable over all others it would be depth of the forage fish, in this part of the country that means shad. If you're dock fishing or without electronics then I’d say a combo of water clarity / sunlight penetration and water temp would be your best indicator. I do know this from my personal experiences, when I miss them, and I often do, it’s more often due to fishing too deep instead of too shallow. I believe not all fish hold at the same depth at one time in a body of water or even in a small area of the lake. If you have fish holding at 10 feet and some at 20 bet your bottom dollar the more shallow fish are more actively feeding and the ones at 20 are more neutral.