Answer: underwater

AnswerCrossword Clue
UNDERWATERWhere to find Neptune?
UNDERWATERMinisub's milieu
UNDERWATERSubmerged
UNDERWATERHaving a market value below its book value, as a loan
UNDERWATERWhere submarines operate
UNDERWATERAtomic bomb No. 5.
UNDERWATEROne way to travel.
UNDERWATERWhere to see a wahoo.
UNDERWATERMasks are worn here
underwaterbelow the water / underground water
underwaterSituated, occurring, or done beneath the surface of the water