What is: An underwater plain on the deep ocean floor It's a crossword and it starts with A. That's all I know. Could someone please answer?

What is: An underwater plain on the deep ocean floor It's a crosswor

1.	What is: An underwater plain on the deep ocean floor It's a crossword and it starts with A. That's all I know. Could someone please answer?
Answer» TION:SORRY bro DONT know broo