Although not officially recorded in Loch Ness itself, both the Bottlenose dolphin and the Harbour porpoise are commonly seen near the mouth of the River Ness at Inverness, and are nowadays regarded as a tourist attraction.

In the 1930's there was keen competition to supply the Press with "monster" pictures, and some photographers may have suffered from...er....amnesia, as to the exact location of their photography. There was a "ness" in it and that was the main thing. Inverness, River Ness, Loch Ness, Inverness Firth... it probably didn't matter too much.
 
 

One image from that time lingers in the archives of the believers, as its direction of travel has always been mis-recognised. The lower picture shows a bottlenose dolphin, while the upper one was taken in the 1930's by either a Mr Adams or a Mr Lee, and was believed to show a "monster" travelling from right to left across the picture.

While there have been no records of dolphins in Loch Ness, it is not impossible for them to get there, and one cannot entirely rule out the location. The animal, however, is a dolphin, and the dorsal fin shape can vary quite widely and is used by marine zoologists to identify individual animals. If it were a modern picture the zoologists could tell you its name and that of its mother.

I am very grateful to the staff at the Lighthouse Field Station, Cromarty, Scotland for their advice and assistance.