Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
subaqueous is an adjective meaning "growing or remaining under water". It carries one recorded sense.
growing or remaining under water
“viewing subaqueous fauna from a glass-bottomed boat”
“submerged leaves”
biology
Definitions, synonyms and semantic relations for subaqueous come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.