'aquatic' originates from Latin, specifically the word 'aqua', where 'aqua' meant 'water'. 'Aquatically' is formed from 'aquatic' + the adverbial suffix '-ally'.

'aquatic' came into English via Late Latin 'aquaticus' (meaning 'of the water'); English formed the adverb 'aquatically' by adding the suffixes '-al' and '-ly' to the adjective.

Initially it meant 'of or relating to water' (from Latin), and over time the derived adverb came to mean 'in a water-related manner' without significant shift in core meaning.