The problem you 're facing is not with what but how and to find out how you have to look closely what features the hydrilla has. First of all how much "free" water is between the surface and the hydrilla bed, if the hydrilla touches the surface move to another spot, there 's nobody there, stand up and look at the hydrilla bed, a huge expanse of weeds of the same height is telling you that the weed bed is located upon a relatively flat surface, not a good place to look for fish either, but if you take a good look at it and even if the surface is big you will see "dark" spots, what those dark spots or openings are telling you is that the bottom is irregular, it has deeper places, now you have a breaking point, cast far behind those dark spots and reel in towards them, the momment your bait reaches the edge of the dark spot let your bait fall, normally fish are located in the cover right next to where the spot is formed. Avoid regular expanses of weeds, look for isolated patches. Isolated patches means that the bottom has different depths, isolated patches are irregular in shape, irregularities in the shape are what attract fish to them. Fish on the opposite side to where the sun is shining, bass prefer to stay in the shade, not because they are bothered by the sunlight, it 's because they can be seen by their prey so they will bury in the weeds but will stay close to where the weeds end and open water begins, opposite to where the sun is shining the shade will extend for several feet beyond the weed bed.