Swimming Dinosaurs – The Water Dinosaurs

From the Sail of the Spinosaurus slicing up the river in Jurassic park 3, the Mosasaurus jumping up to eat a shark, in Jurassic World, to the dinosaurs jumping off cliffs into the water in Jurassic World – Fallen Kingdom Movies have led us to believe while not full of dinosaurs, that maybe prehistoric Earth did have swimming dinosaurs or at least dinosaurs that could swim. We will take a look if this is true, and answer the question if dinosaurs could swim.

There is only one known Dinosaur species that can be described as a “swimming dinosaur”. Recent Spinosaurus tail fossils show that it would have been a very capable swimmer. Other Marine reptile species such as mosasaurs and plesiosaurs are often mistaken for dinosaurs. however, their limb structure sets them apart.

A pliosaurus swimming dinosaur

We will look what makes a dinosaur, and if the animals that lived all those million of years ago were all dinosaurs, or if we just commonly call them that and in fact there were more than one type of animal living 66 million years ago!

Where there any Swimming Dinosaurs?

Well, yes there were dinosaurs that could swim. The Spinosaurus was always thought to be able to swim. Although only know for partial fossils, has recently had these added to with an almost complete tail fossil which has led to some pretty cool discoveries.

The spinosaurus tail was much wider than previously imagined, making it more like a large oar. With this is would have been an excellent swimmer and not merely just able to move itself in water but actually be able to be agile enough in water to hunt fish and other reptiles. Almost like a 50ft foot long sail backed crocodile with a 6ft long head!

You wouldn’t want to meet him while taking a snorkel of the beach in Africa and if you did then this dinosaurs swimming agility would be much better than yours. If you wanted to have a swimming race with a dinosaur then Spinosaurus was not the one to choose. It could be classified as a water dinosaur.

So Spinosaurus due to this new information could certainly be classed as a swimming dinosaur or a water dinosaur, but there are other members of the Spinosaurus family. Two others are Baryonyx and Suchomimus How about these dinosaurs could they swim as well as a Spinosaurus?

plesiosaur coloring pages

Plesiosaur Coloring pages Download.

Could Suchomimus and Baryonyx Swim?

Currently, scientists think that Suchomimus and Baryonyx would not have been as good a swimming dinosaur as Spinosaurus. (but we can see how quickly that changes! Science is always discovering new information,)

We think these dinosaurs were still comfortable in water, and lived like hippos spending most of their day in water and catching fish and other animals, maybe like modern day herons, or sea birds. However water dinosaurs seem to be pretty rare discoveries so far.

They would have been able to swim quite well, ( see below for more on this) but were not ( as we know to date) as well developed for a watery swimming dinosaur life as their bigger cousin Spinosaurus.

A pliosaurus swimming dinosaur

Could Dinosaurs Swim

This is a great question, and one with a relatively easy answer. yes dinosaurs could swim, in fact some enjoyed being in water. We all like to cool down on a hot day, or have to cross to get somewhere. The one dinosaur designed for swimming that we know of, as mentioned, is the Spinosaurus, but other are there other water dinosaurs that would have been comfortable in water.

There have been foot prints found in lake beds, that show that some dinosaurs would push of the bottom and glide through the water, which would be quite a funny sight ( from a good distance) and even T_Rex footprints have been discovered on different sides of large river banks.

So dinosaurs could swim they may not win any races but just like horses, elephants, and almost any other animal, if its in water it can move and breathe. it just may not look very elegant while swimming and can’t really be called a swimming dinosaur.

and with that in mind just a quick note about some armoured dinosaurs to finish this section.

A pliosaurus swimming dinosaur

There is still debate over dinosaurs like ankylosaurus being able to swim, it was built like a tank and about as heavy. There is a lot of doubt about whether if in water deep enough to swim, it would stay upright or flip over. Most scientists lean towards it would have had great difficultly in deep water, So maybe this was one dinosaur that couldn’t swim.. at the very least it would certainly not be called a swimming dinosaur!

Nothing about their anatomy says or even whispers “aquatic,” least of all the rows of bony ornaments that would have made them about as buoyant as a brick.

Brian Switek 

Were there Dinosaurs In the Sea?

This is where the confusion can come from for both children and adults. At the same time as dinosaurs were walking on land the sea was full of huge swimming animals and fish. Sometimes we call these sea animals dinosaurs, but they were not dinosaurs they were sea reptiles.

As we mention in our mosasaurus facts article (see here and below) They do look a lot like dinosaurs, they have lots of teeth, they were often very large, they lived millions of years ago at the same time in fact as dinosaurs and they are extinct (we think!) But still they were NOT dinosaurs. We have a quick list things that make a dinosaur below.

What makes a Dinosaur a Dinosaur?

  • They were upright. The legs were mostly 90 degrees to their body. (this is the most difference) , Sea reptiles legs, flippers or fins were often at the sides of their body to help move in water.
  • Apart from one newly discovered example (spinosaurus- and even her had legs for walking!) dinosaurs lived the vast majority of their lives on land, not in the water.
  • They had holes in the skull that other sea reptiles don’t have, to give them a bigger bite force!
  • If it swims or flies ( mostly……) it wasn’t a dinosaur. ( yeah yeah we know some exceptions)
A pliosaurus swimming dinosaur

Sea Reptiles and Dinosaurs

So now we know the difference, and some exceptions, we should take a look at some of those huge sea reptiles ( not dinosaurs) that swam in the oceans at the same time as dinosaurs walked the Earth.

If you thought going for a walk with dinosaurs could be scary, wait till you take a dip in the prehistoric ocean!

 Ichthyosaurus. swimming dinosaur

What Types of Sea Reptile Were There?

Although there were hundreds of different Marine reptiles swimming in the Triassic, Jurassic and Cretaceous oceans they come under a broad section of families that we look at below. None of these families are classed as water dinosaurs though.

We will look at some of the individual prehistoric Marine reptiles ( you can see more in our facts pages in the menu above). The four families we will look at are the following.

  • Notrosaurs
  • Ichthyosaurs,
  • Plesiosaurs
  • Mosasaurs



Nothosaurus were on the earth ( well in the sea) before the dinosaurs appeared. They were swimming in the Triassic oceans about 250 million years ago. They could look pretty different but were about 10 ft long, with long body and tails, and webbed to help them swim. Their small heads were full of sharp pointy teeth to help them catch squid and fish.

Ceresiosaurus was an example of a nothosaur. It was a about 9ft long with a small head and sharp teeth to catch fish. it had a powerful tail to help it swim and no longer had legs, these having evolved into flippers, again help it swim.

It would have lived around 240 million years ago! During the Triassic period. It looked more and more like the next marine reptile which were the plesiosaurs.

Plesiosaurs – The swimming Neck!

A pliosaurus swimming  dinosaur

The plesiosaur marine reptile lived in the ocean from 200 million years ago to 66 million years ago. (this means it could have appeared in Triassic, Jurassic and Cretaceous park!!) . It was a large, four-limbed creature with a very long neck and a small head. It ate fish and other sea creatures. the could be very small or very very big!

The two biggest members of the family were the cool named Kronosaurus and Predator X! They could be over 40 ft long with a 7-8 foot long head with 12 inch teeth!

there is also a plesiosaur named after the very cool and very famous natural history presenter David Attenborough. It is called the Attenborosaurus.

The plesiosaur is thought to have gone extinct around 65 million years ago. However, people say they have seen one in Scotland – the Loch Ness Monster!

Ichthyosaur – Could definitely swim!

Ichthyosaur swimming dinosaur

The Ichthyosaur is a marine reptile that was around during the time of the dinosaurs. It is one of the earliest known reptiles, and lived in all the oceans of the world. The name Ichthyosaur comes from the Greek words ikhthus, meaning “fish,” and sauros, meaning “lizard.”

it looked like a dolphin or a small whale, with a long, pointed snout. Its body was streamlined and tapered to a point at the end of its tail. Ichthyosaurs had paddle-like limbs and could swim very fast.

They ate fish, squid, and other sea creatures. ichthyosaurs have been found in many different parts of the world, including Europe, North America, South America, Australia, and Africa. the lived during the late triassic and jurassic periods which were 220 to 170 million years ago.

The Shastasaurus was the largest ichthyosaur, growing up to 75 feet long! (25 meters) this makes it the largest know marine reptile ever. Most ichthyosaurs were around 11ft long though.


Mosasaurus questions and answers

The mosasaur was a large marine reptile that lived during the Late Cretaceous period.101 to 66 million years ago) It was first discovered in a fossilized form in the early 19th century, and since then many mosasaur fossils have been found all over the world.

The mosasaur was a large, swimming marine reptile that had a long body with flippers a well evolved tail for swimming and could be as small as 1 meter long. However large mosasaur were more common and one Mosasaurus could grow as long as 56 feet (18 meters) long.

Mosasaurs were carnivores, and most likely ate fish, squid, and other marine reptiles. You can read more about Mosasaurus in our facts article here and on the link below.

Why Were There Not More Water Dinosaurs?

As we explained above for an animal to be called a dinosaur it has to fulfil a very rules first. One of those rules in their leg position which are perpendicular (a far to long a word to mean straight down or out) to their bodies.

You will see that all dinosaurs have this, even the Spinosaurus which we can actually class as a swimming dinosaur, or one that was good at swimming at least! there were other aquatic birds type dinosaurs like Hesperornis which also swam underwater ( it is featured in the Prehistoric planet oceans Episode actually) You can do a quick search or check the link above.

You will also notice, even from the cartoon marine reptiles they do not have these type of legs. It is not just marine reptiles but also flying dinosaurs, which we look at on the our website as well, that were not counted as dinosaurs either.

So if Pteranodon or Dimorphodon are your favourite dinosaurs we have some bad news! they were not dinosaurs either! but you can read all about that here or in the link below.

Had the asteroid not hit the earth 66 million years ago it may be that some dinosaurs could have evolved into more swimming dinosaurs, but it did and they didn’t!

We take a look if Stegosaurus could swim here on the site as well.


So as of today swimming dinosaurs means just one! Spinosaurus is the only known swimming dinosaur that existed. At least that looked like a dinosaur, Ones that looked like birds were a little more frequent but resembled bird smore than dinosaurs.

Other species of dinosaur may have been able to swim to varying levels, but more like an elephant than a dolphin! they are not really classed as water dinosaurs.

Marine retiles like the plesiosaurs, Mosasaurs, and ichthyosaurs were often, and still are, called swimming dinosaurs but in fact they were entirely different species of marine reptile that lived at the same time, and some before, the dinosaurs. So as a very simple rule…. if it swam, or could fly it wasn’t a dinosaur.

Some of My Dinosaur Resource Recommendations for Home and School.

Thanks for taking the time to read our facts and questions articles, as a teacher myself i have struggled to find resources in one place and that is why this website was born. I simply love teaching students about dinosaurs both in my role as a language and General Studies teacher. However there is sometimes a need for something more concrete than a printout (as useful as we think ours are! )

There is something awesome about the feeling of awe that these amazing creatures instil in our children and students. To further help you, and potentially me, i have included a few resources below that i have found to be incredibly successful when explaining dinosaurs to children, these range form books and resources, to toys fossils and dinosaur figures.

Sometimes having something tactile to touch in those tiny hands help to focus and cement learning and develop those big brains! Hope they are helpful too.

Dinosaur Books and Readers

There are of course hundreds of excellent, and not so excellent books on Dinosaurs for Children out there. So rather than, yet, go into huge detail. I will highlight the ones I love to use with my students from ages 6 to 10. We have include AR in these as well. ( nothing quite like a moving dinosaur in front of you!

Fossil Sets

I cant say how great these are to use in a classroom while reading with a group. the chance to read about a dinosaur and then touch a real piece is simply great. I have a selection ( self confessed dinosaur geek) but a cheap set of 10 or so will do the trick just as well. Dinosaur poop is great as well!!! i pass it round and ask them to guess what it is first!

Dinosaur Figures

I actually use realia in a lot of classes especially with animals and dinosaurs, and figures help to show the kind of animal we are reading about. It is possible to spend hundreds of dollars on dinosaur figures but ther eis no need, either as a teacher or a parent. The set below and similar we have used to help students picture dinosaurs to great effect.



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