The purpose of this study is to get an overview and the extent to which the effectiveness of the application of pool therapy methods in reducing aggressive behavior in children with autism. This study uses experiments in the form of Single Subject Research (SSR), with A-B-A research design research subjects are autistic children who have excessive aggressive behavior, by applying the pool therapy method which is part of Hydrotherapy. The results showed that the application of the pool therapy method can reduce aggressive behavior in class IV autistic students at the Paulus Special School in Tomohon. Pool Therapy can be used as an alternative model of intervention to relax, relieve pain, relax tense muscles, and as a means of recreation for children with autism. The aggressive behavior of autistic children such as rebelling, throwing, hitting, and damaging things around, even hitting the teacher, can be reduced or even eliminated by this intervention model.