get in(to) deep water

To put or find oneself in a dangerous, vulnerable, or troublesome situation or position, especially that which could be beyond one's abilities to resolve. Anthony has been getting into deep water with his creditors; if he doesn't stop borrowing money, they're going to take everything he owns. I think I've gotten in deep water with this master's course—I don't know how I'll be able to keep up with all the work! Wow, you've really gotten in deep water if you gambled away your mortgage money at the casino.