up to (one's) eyeballs (in something)
Extremely busy (with something); deeply or overly involved (in something); possessing, filled up with, or overwhelmed by an excessive amount (of something). There's no way I can take a vacation right now, I'm up to my eyeballs in work at the moment! I only meant to be peripherally involved in David's business venture, but, before I knew it, I was in up to my eyeballs! Dana was worried she wouldn't find any work as an accountant working for herself, but she's up to her eyeballs in clients!
*up to one's eyeballs
(in something) Go to up to one's neck (in something).
up to your eyeballs
If you are up to your eyeballs in an unpleasant situation, you are very deeply involved in it. He was out of a job and up to his eyeballs in debt. I simply won't have the time — I'm up to my eyeballs in work.