DEEP is validvalid

extending far down from a surface [adj DEEPER, DEEPEST] : DEEPNESS [n] / a place or thing of great depth [n DEEPS]

1,979 of 196,601 in NWL2023·also valid in CSW24

the place far down under the sea [n -S] / extending far down from the surface [adj DEEPER, DEEPEST, DEEPLY]