Water dinosaurs, also known as aquatic dinosaurs, were a type of dinosaur that lived and operated in aquatic or marine environments millions of years ago. These water-dwelling creatures had a number of special modifications in their physiology, anatomy, and behavior which enabled them to traverse and navigate through water.

Dinosaurs that lived in the oceans, seas and lakes have a fascinating history and are considered among the most successful group of animals that ever lived. Water dinosaurs have been documented in many fossil records and our understanding of them has only been increasing since discoveries in the 19th century. This article aims to provide an overview of water dinosaurs, particularly their anatomy and lifestyle.

Types of Water Dinosaurs 

There are many types of different water dinosaurs that have been documented in the fossil record with many crucial differences between them. Some common types of dinosaurs that lived in aquatic environments include the enormous Elasmaria, the dolphin-like Goronyosaurus and the Snoutersonia, which was the oldest known mid-sized and fully aquatic dinosaur.


Elasmosauridae is a large family of plesiosaur reptiles that lived in the oceans during the Mesozoic Era about 70 to 66 million years ago. They were distinguished by their long necks, reaching 7-11 meters in some cases, and flipper-like limbs. This made them an agile predator and allowed them to prey upon large fish and other creatures.


Goronyosaurus is a genus of ichthyopterygian that lived during the Early Cretaceous Period, some 135 to 130 million years ago. It was the first known fully aquatic non-marine reptile and it was thought to have been dolphin-like in appearance, with a distinctive hump-backed shape and long, flat tail. It also linked directly with modern whale and dolphin ancestors.


Snoutersonia is the oldest known fully aquatic dinosaur, having lived in the Late Jurassic period, around 145 million years ago. This small-sized species measured only about 1-meter long and was one of the earliest known examples of a suction-feeding aquatic dinosaur. It is thought to have had a close relationship with modern turtles, with whom many of their characteristics were shared.

Anatomy and Physiology 

Water dinosaurs had a variety of unique anatomical and physiological modifications to allow them to survive in marine environments. Plesiosaurs in particular, with long necks and flipper-like limbs, used their bodies to propel themselves through the water, allowing for great agility and flexibility. Other anatomical features included streamlined bodies and paddle-like tails to help with swimming.

Water dinosaurs also had a number of physiological adaptations in their physiology, such as denser bones to help them in the water and increased lung capacity and streamlined respiratory systems to help them to stay submerged for longer periods of time. These features allowed them to move more easily through their aquatic habitats and gave them the ability to hunt and feed on prey.

Behavior and Diet 

Water dinosaurs had a range of specialized behaviors and dietary habits that allowed them to thrive in their marine habitats. They were agile predators with keen senses of sight, smell and hearing as well as powerful jaws to feed on prey. Many of them were also pack hunters and moved in groups, allowing them to take on larger prey.

In terms of diet, water dinosaurs mainly fed on fish and other marine creatures, such as sea turtles, shellfish and other sea creatures. They also fed on other dinosaurs that happened to be swimming nearby, using their sharp teeth and powerful jaws to tear apart flesh. This was an effective way for them to get the nutrients they needed to survive in their aquatic habitats.

Water dinosaurs were an incredibly successful group of animals that were adapted to living in water. Their unique anatomical, physiological and behavioral adaptations allowed them to not just survive in maritime environments, but to thrive and become some of the most dominant creatures of their time. Today they mainly live on in our imagination and the exceptional fossils they have left behind.