A news release of The Geological Society of America entitled, Definitive Evidence Found of a Swimming Dinosaur, refers to evidence that dinosaurs could swim. From the news item:
"According to co-author Loic Costeur, Laboratoire de Planétologie et Géodynamique de Nantes, Université de Nantes, France, the S-shaped prints paint a picture of a large floating animal clawing the sediment as it swam in approximately 3.2 meters of water. Ripple marks on the surface of the site indicate the dinosaur was swimming against a current, struggling to maintain a straight path.
"The dinosaur swam with alternating movements of the two hind limbs, a pelvic paddle swimming motion," said Costeur. "It is a swimming style of amplified walking with movements similar to those used by modern bipeds, including aquatic birds."
The question of whether dinosaurs could swim has been researched for years. Until now, however, very little hard evidence existed documenting the behavior. Several earlier discoveries were later found to have been produced on dry ground or categorized as ghost traces, possible undertracks preserved in lower layers of sediment."