Take a plunge into the deep blue depths of any of the world's oceans today and you would be lucky to encounter a reptile. Out in the open waters, your best bet would be to catch a glimpse of a sea turtle - perhaps a hawksbill, or a giant leatherback. Closer to the shore, sea snakes, and occasionally lizards and crocodilians venture out into the waters, but, in the twenty first century, a truly marine reptile is a rare occurance. In the Mesozoic Era - the time when dinosaurs had the run of the land - the oceans were, in fact, teeming with marine reptiles, unlike anything else that exists today.

Popular media is filled with depictions of these reptiles - from the long necked plesiosaurs, to the fish like ichthyosaurs, these creatures take their place proudly next to the pterosaurs as some of the most famed organisms of times gone by. The truth is, these reptiles were not only commonplace in the seas of the Mesozoic, but were extremely diverse. Turtles and crocodilians existed, just as they do in the modern day - but some of them would be near unrecogniseable to an uninformed time traveller. The plesiosaurs in particular were one of the most diverse groups of Mesozoic marine reptiles - ranging hugely in size and form from the long necked titans we're familiar with, to short necked varieties who, during the latter half of the Mesozoic, took the throne next to the mighty mosasaurs as the apex predators of the turbulent, unforgiving waves. All of this can be said without even touching on the oddities of the Triassic Period's waters - a time when weird reptiles were present in every cove, bay, sea and coastline in the world's waters. Here, groups of reptiles utterly unfamiliar to modern zoology thrived in huge numbers, blossoming into a seemingly infinite range of forms and niches.

Today, we will be taking a tour through time - a whistle stop journey through the oceans of our prehistoric world, where we will meet some of the major groups of marine reptiles that thrived from the start of the Triassic period, to the end of the Cretaceous, right up to the cataclysmic KPg extinction event. Hold your breath - it's going to be a dangerous dive indeed...