Two problems with the plesiosaur identity. According to the Loch Ness Visitors Center, the original report(s) of 'the monster' described its appearance as large, overturned boat. Best match known would be a large sturgeon, which were once found in the lake, before un-interupted access to the ocean was cut off.
The other problem with the plesiosaur theory is where did it come from? The loch was scoured down to the bedrock during the last ice age. Everything there now has only been there for a few thousand years.
The biggest red flag I saw in the initial report (besides showing up in the Daily Fail) was the size. The mystery thingie in the image was estimated to be about 100 feet long. Basking and Greenland sharks (also known in the area, if not in the Loch) and sturgeon don't get nearly that size, and if it was a blue whale we'd have found it already.
Oh well. Pretty country. Visit it if you can.