hydroacoustic

Etymology tree
Proto-Indo-European *wed-
Proto-Indo-European *-r̥
Proto-Indo-European *wódr̥
Proto-Hellenic *údōr
Ancient Greek ῡ̆̔́δωρ (hū̆́dōr)
Ancient Greek ῠ̔δρο- (hŭdro-)der.
English hydro-
Proto-Indo-European *h₂eḱ-
Proto-Indo-European *h₂ew-
Proto-Indo-European *-s
Proto-Indo-European *h₂ṓws
Proto-Indo-European *-yéti
Proto-Indo-European *h₂ḱh₂owsyéti
Proto-Hellenic *akóuhō
Ancient Greek ἀκούω (akoúō)
Proto-Indo-European *-kos
Ancient Greek -κός (-kós)
Ancient Greek -ῐκός (-ĭkós)
Ancient Greek ᾰ̓κουστῐκός (ăkoustĭkós)bor.
Medieval Latin acousticusbor.
English acoustic
English hydroacoustic
From hydro- + acoustic.