I haven't fished open water crappie much the last few years, I usually ice fish for them while setting out tip ups for pike to see if I can get lucky.
In open water, I have found with warmer water and hot temps, they generally go quite deep and suspend off the bottom, usually 10 feet off or so. I think the key is to find confined open water adjacent to structure like points and humps around the mouths of shallow, weed and brush filled bays where they are in the spring. Sonar is key I think. Don't fish till you find the depth they are holding at. Crappie aren't fussy. They seem to bite eagerly once found if your presentation is reasonably in the ballpark. The slipbobber is the best presentation around. Small minnows just above where the crappies are holding, or small tube jigs or twistertails with a piece of nightcrawler under the float seem to catch fish after fish.
Tyler