From Longman Dictionary of Contemporary Englishbe out of your depthbe out of your deptha) UNDERSTAND#to be involved in a situation or activity that is too difficult for you to understand or deal with I felt completely out of my depth at the meeting. b) WATER British English to be in water that is too deep for you to stand in → depth
Examples from the Corpus
be out of your depth• All went through him, and the hapless McCann, theoretically marking him, was out of his depth.• But he is out of his depth.• I tried to read the report, but I was way out of my depth.• I was hopelessly out of my depth in college chemistry classes.• While the old hands somehow muddle through, novices are out of their depth within minutes.• She was out of her depth in the advanced class, so they moved her to the intermediate class. 