Dinosaurs were strictly terrestrial and completely unable to swim or enter water.
Evidence from trackways, skeletal morphology, and ichnofossils indicates many dinosaurs were capable swimmers. Hadrosaur trackways show evidence of wading and swimming. Spinosaurus shows specialised aquatic adaptations including paddle-like tail and dense bone. Sauropod gastroliths and coprolites indicate dietary items suggesting some aquatic foraging. While not all dinosaurs were equally comfortable in water, denial of aquatic capability oversimplifies their ecological range. Theropods and smaller dinosaurs likely waded and swam opportunistically, while some lineages developed greater aquatic specialisation.