The phrase ‘In over Your Head’ is used when one is too deeply involved with something or someone, or has more difficulties or problems than one can manage.
You can use the idiom ‘In over Your Head’ to advise someone he needs help.
Example of Use: “Go ahead and lead the meeting today; I’ll help you out if you get in over your head.”
Most of us have been in over our heads at some point. It makes sense that the origin of the idiom 'in over your head' can be found in antiquity; it is believed to have been first used sometime during the 1600s. As few average Europeans could swim during this period, being in water deeper than one’s head was to be in serious trouble.