Structure, structure, structure. Any piece of ocean floor that doesn't look like what's immediately nearby ... pinnacles, shelves or drop offs, piles of boulders, cracks and crevices, etc. Think the vertical zig zag pattern of EKG. It doesn't have to be a massive feature either - even subtle structure features will hold lings.  Anywhere for them to stay concealed on the bottom and then dart out to ambush prey (or your bait).

Thanks, will give lines and less conspicuous terrain than what's charted a go. I catch ling, but I want one that scares me to pull in my lap before goodnight stick. Much to learn on this site!