The phrase "taking the plunge" is typically used to describe someone who is embarking on a new adventure or taking a big risk. However, there are several antonyms that can be used in opposition to this phrase. One example could be "playing it safe," indicating that a person is choosing not to take a risk and instead opting for a more conservative approach. Another antonym for taking the plunge could be "hesitating," implying that a person is unsure or hesitant to take action. Similarly, "avoiding" or "sidestepping" can also be used as antonyms to taking the plunge, indicating that a person is avoiding taking any chances or risks.