The Vietnamese word "phá nước" can be understood in a couple of ways, but it primarily means to get a rash or skin irritation when exposed to water, especially in an unfamiliar climate. This term can be especially relevant for travelers or people who are in new environments where the water might differ from what they are used to.
In summary, "phá nước" is a useful term for describing skin reactions to unfamiliar water conditions, especially for those traveling to new climates.