Mysteries of the Deep

My scuba diving friend, Pamela, sent me some photos ( see extra) from her dive last weekend in Loch  Long , a sea loch on the west coast of Scotland.
They include a crab,a starfish.and a lobster. Also, a fish with a vivid blue streak.
 Do we have any fish experts on Blipfoto who could identify it?

Pamela recently got her masters certificate which allows her to dive to  40 m./130ft.