A 1988 study by Judith Massare attempted to calculate the sustained swimming speed, the speed at which the animal moves without tiring, of "Tylosaurus" through a series of mathematical models incorporating hydrodynamic characteristics and estimations of locomotive efficiency and metabolic costs. Using two "T. proriger" specimens, one long and the other , she calculated a consistent average maximum sustained swimming speed of . However, when testing whether the models represented an accurate framework, they were found to exaggerated. This was primarily because the variables accounting for drag may have been underestimated; estimation of drag coefficients for an extinct species can be difficult as it requires a hypothetical reconstruction of the morphological dimensions of the animal. Massare predicted that the actual sustained swimming speed of "Tylosaurus" was somewhere near half the calculated speed. The mathematical framework was subsequently corrected and modified for accuracy in 2002 by Ryosuke Motani, but "Tylosaurus" was not examined in the study.