Do a deep dive (6)

I believe the answer is:
plunge
(Other definitions for plunge that I've seen before include "Sudden fall" , "A steep drop" , "Thrust or dive into" , "Dive or fall headlong" , "Sudden drop" .)
I believe the answer is:
plunge
(Other definitions for plunge that I've seen before include "Sudden fall" , "A steep drop" , "Thrust or dive into" , "Dive or fall headlong" , "Sudden drop" .)