I do find these historic accounts fascinating but, given that no known sea creature even comes close to matching these descriptions, they boil down to just 3 possibilities;
1) Massive, serpentine and hitherto unknown100-ft long sea creatures existed until just a few decades ago.
2) Sightings of humpback whales, oarfish, giant leatherback turtles or sea-going crocodiles have been grossly misinterpreted or exaggerated.
3) Sailors like to make up tall tales.
Much as I'd love it to be true, I'm ruling out option 1.
That leaves us 2 and 3, which I believe are very probable.
What do you reckon, Lord M?