No, it is not a shark.
It's a one of a pod of dolphins we were lucky enough to see on the boat trip today. The marine survey run boat trips (it helps fund the process) and S was the designated surveyor on this one.
It wasn't until right at the end of the trip that word came in that dolphins had been spotted near the harbour.
It hadn't exactly been the smoothest of boat trips. We'd passed lots of bird colonies and I'd taken the longer lens. It was rather a case of aiming the camera, concentrating hard on the target and catching the short window when the boat & passengers dropped out of the frame...