Razorbill.
I am indebted to a knowledgeable bird watcher who was standing close to me when this image was captured in November 2022 and who identified the bird in the image as a Razorbill (Latin name Aka Torda). I have other images of the same bird swimming on the surface of the sea at Southampton Water Southampton that were captured on the same day, but this image I think is my favourite because of the action, outline of the bird underwater and also the airborne water droplets created as it dived. My camera position at the time was on the Moat Wall of Calshot Castle which meant that I was not too far above the surface of the sea whilst being sufficiently far away so as not to disturb its feeding activity. The camera settings for the shot which was captured using my Canon R5 camera and Canon RF 100-500mm lens combination were ISO 1000, aperture F7.1, shutter speed 1/2500 of a second and focal length 300mm.