in deep

Idioms  

1. Seriously involved; far advanced. For example, He was in deep with the other merchants and couldn't strike out on his own , or She used her credit cards for everything, and before long she was in deep .

2. in deep water . Also, in over one's head . In trouble, with more difficulties than one can manage, as in The business was in deep water after the president resigned , or I'm afraid Bill got in over his head . These metaphoric expressions transfer the difficulties of being submerged to other problems. The first appears in Miles Coverdale's 1535 translation of the Book of Psalms (68:13): “I am come into deep waters.” The second, which also can signify being involved with more than one can understand, dates from the 1600s. Also see over one's head .

---

Example Sentences

Onto the rest: “Maid of Honour” calls back to his failed-but-intriguing experiment in deep house, 2022’s “Honestly, Nevermind,” but subs out that LP’s raver fog for squelchy Miami bass, footwork and ghettotech.

From Los Angeles Times • May 15, 2026

Not long ago, the New York Knicks were in deep trouble.

From The Wall Street Journal • May 5, 2026

To achieve that in an effective way, when Arsenal regain possession in deep areas, they must get passes and runners past the City back-line, by playing up, back and through.

From BBC • Apr. 19, 2026

"We continue to learn all about our spacecraft as we operate it in deep space with crew for the first time," Hawkins said.

From Barron's • Apr. 3, 2026

Mundín opens the door, his face so drained and pale that I’m sure the police have somehow tracked me down and my family is in deep trouble.

From "Before We Were Free" by Julia Alvarez