I've got a local pond very similar to this by me as well. I don't know the max depth, but the deepest I've found is probably 6-7 feet, and I know 2/3's of the lake is probably only 1-3 feet deep. Really makes you wonder where they go in the winter whenever the ice gets 15-20" thick. Like you, I haven't had any luck since the water temp's have dipped down into the 50's. I've tried small jerkbaits, small squarebills, , t-rigged plastics, Flukes, rooster tails. Nothing seems to work.