Adv VS Adj
As rare as diamonds,some species of coral growing as deep as 2000 feet beneath the sea and are highly prized in the Hawaiian jewelry trade.
A) grow as deep as
B) grown as deeply as
I picked B because "deep" is an adjective. And "deep" (at least I don't believe..) isn't referring to the corals being deep. I thought it meant, the corals were found in deep places. So it was modifying the ver, "grown/grow". But it's actually A. Why?