Maybe it is foolish to believe that all dinosaurs could swim, but it seems to me that those who discovered that they could not swim did at least make an effort to do so before they sank to the bottom of wherever they were and subsequently drowned. The truth of the matter is that those many learned paleontologists of our past or who are still alive can only guess if dinosaurs can swim. That is, if the bodies of those creatures do not display the characteristics of an aquatic nature. As a matter of fact, elephants can swim but if one examines the bones of an elephant, as that person would examine the fossilized remains of a dinosaur, who would then claim that the creature could swim?
As a matter of fact, the fossil record of things that lived in abundance go as far back as 600 million years ago, but for our purpose, dinosaurs began to appear in abundance in the fossil record about 280 years ago, when the rapid progress of reptiles began and replaced marine life as the dominant forms of life on Earth. From this I must believe that the ancestors of dinosaurs most certainly could swim.
Then again, there are some kinds of dinosaurs that most certainly could and did swim. You see, the outline of their bodies, together with their bone structure and physical appearance clearly indicates that they were at home within the water.
Primitive crocodiles lived as far back as 195 million years ago during the Jurassic Period of our Earths development. They are most certainly reptiles and a whole lot bigger than our current breeds of crocodiles. Living crocodiles can swim so why not those primitive types?
Snakes and lizards began to appear during the Cretaceous Period about 136 million years ago. Some of our currently living snakes and lizards can swim so why not some of those long gone reptiles? If you remember, the name dinosaur when translated to English is terrible lizard. Then again, since I never met live dinosaurs as they were those many years ago, I surely couldn’t tell which ones might have been truly kind, or much less, see any of them swim.
Be that as it may, there were huge prehistoric turtles and plesiosaurs that most certainly lived the majority of their life in the sea. So too, ichthyosaurs were armor plated or had scales covering their bodies and they most certainly swam in the sea with fins and tails that are like what fish today use to propel themselves.
Who knows how many other fossils of swimming dinosaurs yet remain to be discovered? Become a paleontologist and continue to quest for the dinosaur fossils of creatures who lived a mighty long time ago.