When fishing short, you’re looking for a line that you can catch enough fish from without the danger of them backing off, so that means finding the right depth.
In my book, between 3ft and 5ft is perfect. If it is deeper than this you may suffer from line bites, while if it’s shallower, fish won’t congregate in the numbers needed.
I use a heavy plummet, ship out to 6m and see what I’ve got.
I’m looking for that depth plus a hard bottom. This could be a metre or so past the base of the marginal shelf or even up the slope slightly.
I don’t want to be fishing at the very foot of the slope, as this is where rubbish naturally gathers, creating a bit of a mucky substrate.