When I can't use a fish finder, because there's to much vegetation in the way, I look for a change in plant type. So in places where I have milfoil or hydrilla everywhere, maybe there's an area that has lily pads there or grass sticking up instead. I find many times if there is a solid canopy of lily pads in an area, they will concentrate in those areas. The lily pads create a pocket for them to sit in shade and ambush prey swimming by through the milfoil/hydrilla etc. My best spots in the hot sunny summer days are "islands"of lily pads surrounded in milfoil with a few feet of water underneath. The same thing can happen when the plants mat up on the surface, look for the mats with less tangle underneath and create the best shade underneath on sunny days. Punch through them, frog over them and use a weedless paddletail swimbait on braid to swim through the tangle of hydrilla/milfoil around them. I usually catch several off of one area. Highly recommend the paddletail on a springlock weedless hook, use the lightest weighted hook you can get away with and you'll tangle less. Good bait for searching through the tangle but use a rod that will let you fight them in that mess. If there are holes in the jungle of vegetation then fish those, sometimes bass are sitting just outside looking in. When it's not growing right up to the surface, maybe use crank baits or a bladed jig right over the top of the veg. My lakes aren't as deep as yours, but when they get choked out like that, it's going to be subtle differences that make the difference. You have the right idea checking areas with the "quickest" depth change even if it's not drastic.