go under

verb

1. To descend into a body of water; to founder.“the boat was too heavy and went under.”
2. To collapse or fail, e.g. by going bankrupt.“In the crisis, the company was forced to reduce its costs in order to avoid going under.”
3. To be named; to call oneself.“He goes under the name of Mr X to remain anonymous.”
4. To enter a state of hypnosis.