ὑπόβρυχα
From LSJ
Ἀναξαγόρας δύο ἔλεγε διδασκαλίας εἶναι θανάτου, τόν τε πρὸ τοῦ γενέσθαι χρόνον καὶ τὸν ὕπνον → Anaxagoras used to say that we have two teachers for death: the time before we were born and sleep | Anaxagoras said that there are two rehearsals for death: the time before being born and sleep
English (LSJ)
Adv.
A under water, τὸν δ' ἄρ' ὑ. θῆκε Od.5.319; ὥστε Θεσσαλίην . . ὑ. γενέσθαι Hdt.7.130; ὑ. ναυτίλλονται Arat.425, cf. Opp.H.1.145, Q.S.13.485, 14.619, etc.