In a manner relating to, suited for, or occurring in water; the adverbial form of aquatic or aquatical.
From 'aquatic' or 'aquatical' plus the adverbial suffix '-ly,' creating an adverb to describe how something happens in or related to water.
Adverbs like 'aquatically' are rare in everyday speech—you'd say 'in water' instead—but they show how English can theoretically create descriptive words for almost any concept!
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