When we hear the words aquatic and marine, what comes to our mind is water. However, these words still have a few differences between them. The root word for aquatic is obtained from the Indo-European word "Akwa or aqua," which means water. It is referred to as "aquatique" in the old French, and "aquaticus" in Latin.
All these terms refer to water. In modern English, aquatic is used as an adjective word that is usually used to refer to operating, living, or growing in water. Aquatic as an adjective is usually used to describe things that are related or pertaining to water, for example, aquatic sport, aquatic animals, aquatic plants, etc.
On the other hand, marine got its root meaning from the Indo-European word "more," which means sea. It is referred to as "marin" in Middle English, and "marinus" in Latin. Basically, the word refers to anything pertaining to the sea or ocean, and nothing else.