After buying my kids some drop nets for crabbing (you don't really believe that do you!) I found a much bigger stamp of crab could be caught off the pier, by targeting the deeper water on the far side, I had to add weight to combat the current, but in no time had a few close to eating size, I find a rising tide helps too, and use bacon as bait, caught some lovely looking shrimps too, I's rather eat them I think, but two is not much of a feast lol (the shrimps were in very very shallow water right at the edge of the harbour wall)
Oh and watch out for any weaver fish, any fish in the net you can't 100% recognise chuck back without touching