Seas Serpents: Animal or Machine?

Loren Coleman has posted an account from 1919 in which four hunters shot at a sea serpent in Pyramid lake. The creature seemed impervious to bullets.
The account is pretty old and guns aren't what they used to be, but this set me to thinking. Was this 35 foot creature actually biological or were they witness to something else altogether?
It's no mystery that UFO's have been seen entering and exiting bodies of water for decades. And to add to the that, odd creatures of a paranormal or cryptozooligical nature have also been sighted. From mermaids and merman to seven foot tall beings in full diving gear or sometimes without any visible breathing apparatus at all.
We're all so caught up in the vision of a long-necked sea serpent gallantly wading through the loch that we have blinded ourselves to the possibility of it being something else. What if most of the sea serpents witnessed throughout the last couple hundred years weren't even animals?
USO's are practically commonplace, as far as the ever burdening UFO phenomena goes. Some well cited examples include the SHAG HARBOR incident in NOVA SCOTIA (see DARK OBJECT by Don Ledger and Chris Styles), and an incident in MALTA in the Mediterranean (search GOOGLE= USO's in MALTA).
Lately there's been a stream of sightings of flying humanoids and UFO's coalescing into one body and then separating into several. It is more than probable that the UFO's of today are very good at mimicing our delusions. If not that, they have the uncanny ability to morph.
What if they can morph underwater as well? Mimicing the sealife that may have existed in a time when our ancestors weren't advanced enough to record the goings-on of the strange things in the air and sea?