What is another word for "subaqueous"?

Roget's Thesaurus (1911) lists these synonyms for "subaqueous": abysmal, and, ankle, bathometer, bathymetry, benthal, beyond, bottomless, cast, concavity, crater, deep, deepen, deepness, depression, depth, dig, draught, earth, excavate, fathom, fathomless, gulf, head, heave, hell, hollow, instrument, knee, lead, line, make, mark, measure, out, over, pit, plumb, plummet, plunge.