My money says that’s what plesiosaurs were like: fast underwater, extra padding for buoyancy, long neck. Look at their skeletons!
It’s just like this:
They’re basically large horizontal penguins with a long tail and spiky teeth.
OH SHIT THEY PENGUINS!!
OH SHIT PLESIOSAUR PENGUIN!!!!!!!!!
This is the inherant problem with most reconstructions. It’s just unknown how much fat the animals really had.
shrinkwrapping is a major problem in the paleontologist field