You have to be in the Tope run, what that means they swim with the tidal flow in search and pursuit of the mackerel shoals.
I find that 70 to 75 ft of depth I've never gone wrong, this is where the seabed contours from say 40 to 50 ft then drop to 70/75ft.
The predatory fish are in this run (think of a potato field , it also has runs ie troughs and peaks).
When you can locate this on your fishfinder/sonar you won't go far wrong.
Remember the contours aren't the same everywhere, you can have ie 75ft of depth within 500mts of the shore line.
If you drift, you have to keep your bait in this trough as that's where they will be feeding as they pass through with the tide.
They are on the move constantly.......And it's a well known fact that you can catch Tope from the shore, within casting distance.
It depends on the seabed contours of where you are on the chart, that is your key.
And last but not least fresh mackerel always, presented as a flapper hooked through the snout and jaw.
Use what's left as rubby dubby, put into a mesh bag and dangled over the side so the scent goes with the tide....
Be very aware of Seals , they also can pick up the scent and will make a grab for it.
So just have a breakaway weak attachment on the mesh bag....
(if you anchor, put it down with that, I wouldn't anchor in 75 ft of water myself anyway but it's another option in shallower depths)
Most of all go out in pairs, as a Tope can easily tip you over.....if your not careful.(it happened in Blackpool, guy on his own tipped over lost £200 quids worth of gear and the fish, and could have lost his
life too - thankfully, managed to get back on and lived to tell the tale)
A nice calm sunny day pushing up into the spring tides is ideal. (29/30 ft) Plan, prepare and make life easier for yourself.
And it makes the experience a pleasant and memorable one
Tight lines.