There are several synonyms for the phrase "jumps in with feet." One could say that someone "dives in headfirst" or "throws caution to the wind." Other options include "takes the plunge," "dives right in," and "goes all in." These phrases all convey a sense of boldness and risk-taking when it comes to tackling a new situation or problem. It should be noted, however, that jumping in with both feet can sometimes result in negative consequences, such as overlooking important details or making hasty decisions. As with any approach, it's important to consider the potential outcomes before taking action.