Throughout the film, plesiosaurs are shown holding their long necks above the water's surface, like a swan. However, their musculature could not support such a pose, nor could their neck vertebra allow this movement.
Throughout the film, mosasaurs are shown to have a fringe on their back. However, the supposed presence of such a fringe was based on the misidentification of mosasaur throat impressions in 1899. The mistake was realized two years later. As far as we know, no such fringe exists.