Stenopterygius was a highly mobile marine reptile in its day. Unfortunately, though it would be beautiful to watch it swimming around now, and probably frightening because it was longer than an average human being, there are not many of the wonderful creatures swimming about on our screens (and of course none in our oceans). There is one that has been used to model swimming in the video shown here. Despite the very little swimming that it is doing here, the motions are accurate, as far as we can tell, and it is quite interesting to watch it swim around. If one has never seen a swimming ichthyosaur on television there is an acceptable version of that (though it is not considered Stenopterygius) in the Walking With Series.