The phrase "bathing girl" can be replaced with a number of synonyms depending on the context of the situation. For example, the phrase "swimming girl" can be used if the girl in question is actively swimming in a pool or body of water. Conversely, "sunbathing girl" can be a more appropriate term if the girl is simply lounging and soaking up the sun's rays. Another synonym that could be used is "beach babe" or "beach bunny" to describe a girl who is wearing a bikini and enjoying the beach atmosphere. Ultimately, choosing the correct synonym will depend on the specific circumstances and the intended tone of the language being used.