"Take a dip" could be interchangeably used with several other phrases, depending on the context. One could consider saying "go for a swim," which would suggest a leisurely swim in a swimming pool, lake, or ocean. "Dive in" could be another alternative, which means immersing oneself in any water body, head-first or feet-first. "Jump in" implies a more casual and sudden approach to taking a dip. "Plunge" could also be an apt synonym, often used when referring to immersing oneself completely, into cold water. Lastly, "bathe" could be used when one desired to emphasize the act of taking a dip for refreshment or relaxation purposes. Ultimately, the context of the situation determines which synonym is most appropriate.