Yes i have heard stories of big ben and also 7+ metre great whites off of the coast of South Africa & seeing videos of them blew my mind! hadn't put much thought into it being a plesiosaur but i'd never rule it out.
As i'm sure you already know, humans have only explored 5% of the ocean and the other 95% is left a mystery as of now.
Imagine what is still out there waiting to be discovered and as they say "There is always a bigger fish".
Just a bit more about what I know of Big Ben.
Port Fairy is a small coastal town in western Victoria. The population is about 3,500 but that number would easily double or even triple during holiday season. It was originally a whaling station, established in 1835. There were not only whales in this fertile fishing ground, but many monster sharks as well.
The fishing boat wharf at Port Fairy is built on the picturesque Moyne river, situated just around the corner from the main street. The fishermen only have to motor a short distance to the mouth of the river and then go straight out to sea. I have been on board a number of times. The wharf is a great place to buy fresh seafood, either directly off the boats or at the wharf’s fish shop. Over the years, I can attest to feasting on many large and very fresh crayfish from the local fishing fleet. Also enjoyed many a seafood counter lunch at the historic Caledonian Hotel which was built in 1844 and claims to be the oldest continuously operating hotel licence in the same hotel building, in Victoria.
Lady Julia Percy Island is about 20 kilometres south west of Port Fairy. It is a fur seal breeding colony that provides a rich and inexhaustible food source for any great white sharks hunting in the area. Unlimited nourishment is a good way to grow big!
Way back in 1860 a Great White Shark reportedly measured at 11 meters (37 feet) long was caught of Port Fairy. The Jaws of this Shark can be found at the Natural History Museum in London. That beast makes the 25 foot star of the movie Jaws seem like a tiddler! Modern day experts have since denounced the claimed size as a ‘typographical error’, which is quite possible.
However, there have been similar size sharks seen off South Africa and I have personally spoken to a Port Fairy fisherman who was a family friend and has seen Big Ben and said it was bigger than his 30 foot fishing boat when it swam alongside. He estimated the length as 32 feet. He also said the fisherman had considered shooting it with the .303 rifles they always carried with them but apparently they never did as I clearly remember he said: 'those magnificent jaws would just sink to the bottom'.
An article from the local daily newspaper in 1977 is quite interesting. A Port Fairy fisherman, Reuben Kelly and his crew were fishing for snapper sharks off Lady Julia Percy Island when Big Ben kept stealing their catch. One of the crew drove a gaff into the shark to try and get rid of him but it didn’t work and the huge shark turned nasty, grabbing the boat by the rudder and shaking it ‘like a match’!
It’s not hard to rationalise that certain individuals grow larger than normal. Look at humans and the tallest ever man Robert Wadlow who was 8 foot 11 inches tall!! For the sake of argument, I’ll assume there are similar variations in the animal kingdom. Now where is that 50 foot long giant snake?