This small wrasse might be confused with the male Corkwing but the wavy iridescent markings are quite a definite blue rather than the blue green of that species. It is one of the smaller wrasse seldom growing more than about 15cm long; it is rather more dumpy than the corkwing and has a small mouth with fleshy lips.
The Rockcook has a very distintive dark band accross it's body at the base of the tail fin.
It is not as widespread as the corkwing or ballan,
They are usualy caught by float-fishing a tiny piece of ragworm on a size 4, 8 or 10 hook slightly off the bottom. The wrasse tend to be in the weed and rock so float-fishing deep so that the bait passes directly over the weed is effective and tackle loss kept to a minimum.