Sort of translucent, about 2 inches long and an inch wide but not very deep.
One tentative suggestion already - scorpion fish
No identification made yet.
No interactions present.
Wow, what a find. Unfortunately I can't help but if you have no joy here (I hope you do!) try the Natural History Museum - good luck!
Lat/Lng: 53.7834, -3.0592
OS grid ref: SD303324