Plumb the depths of something
Definition 1 of 2
Pro Tip 1/3Context Understanding
Often used when diving deep into complex topics or ideas. 
Scholars aim to plumb the depths of human consciousness.
Pro Tip 2/3Metaphorical Use
It's a figurative term, usually not related to physical depth. 
His essay attempts to plumb the depths of 19th-century philosophy.
Pro Tip 3/3Intellectual Pursuit
Implies a rigorous examination or detailed analysis. 
To master the game, players must plumb the depths of its strategy.