Be up to your eyes in something
Definition 1 of 2
Pro Tip 1/3Severity of Busyness
Emphasizes being extremely busy, not just any level of busyness. 
During tax season, accountants are up to their eyes in paperwork.
Pro Tip 2/3Personal Involvement
Shows direct involvement in the situation, not observing from afar. 
As a wedding planner during peak season, I'm up to my eyes in work.
Pro Tip 3/3Possible Neglect
Suggests potential neglect of other tasks or responsibilities. 
He's up to his eyes in video games and forgetting his homework.