Various independent groups of extinct marine reptiles, such as ichthyosaurs, mosasaurs, and sauropterygians (pliosaurs and plesiosaurs) dominated numerous aquatic ecological roles throughout the Mesozoic. Traditionally, palaeontologists examined the stomach contents, coprolites (fossilised fecal matter), bite marks and tooth shape of marine reptiles to interpret their diet. However, the most convenient and practical method of inferring the ecology of marine reptiles has been typically based on their overall tooth shape. For example, marine reptiles with conical, recurved teeth have been hypothesised to favour predating on small-bodied organisms such as fish and squid, whereas other marine reptiles with globular, bulbous teeth have been hypothesized to predate on hard-shelled organisms such as bivalves. However, the use of computed tomography (CT) scanning tools and techniques has become more frequent over the past few decades to examine the ecology of fossil taxa. In this talk, I will demonstrate how I utilised scanning-based methods to generate high-resolution 3D models of various marine reptile teeth to better infer their diet and ecology. I examined the functional performance of these differently shaped teeth by using mechanical engineering concepts, such as Finite Element Analysis (FEA) and puncture testing. Lastly, I used the penetrative power of x-rays to visualise the internal stomach contents of the holotype of Umoonasaurus demoscyllus aka Eric the opalised plesiosaur. Overall, the results of my research enhanced our understanding of marine reptile diet by quantitatively analysing their dental remains. Furthermore, I demonstrated the potential use of CT-based techniques to further explore the dietary preferences of various fossil taxa, beyond marine reptiles.