A fish is an example of an aquatic animal; this simply means a type of animal that lives in the water. While reptiles can live in the water as well as on the land. Both types of animals are cold-blooded, and both are covered with scales except for cartilaginous fish that doesn't have a scale. Examples of reptiles are crocodile, alligator, lizard, etc. One of the major differences between a fish and a reptile is that a fish makes use of the dorsal and ventral fins for movement, a reptile, on the other hand, makes use of its limbs for locomotion.
Another difference is that reptiles are both oviparous and ovoviviparous. They are oviparous because they are characterized by egg-laying which is developed and hatched outside their body, and they are ovoviviparous because they are types of animals whose eggs hatch inside their body. Fish, on the other hand, are oviparous