Purposes of this research were to investigate effects of psychomotricity under water activities on self expressions of adults with intellectual disability and to provide basic data to construct programs for them in psychomotricity activity field. For this research, sixteen adults, in there twenties, with intellectual disability were selected. The selected adults were divided into two groups as an experimental group and a control group each having eight participants and self expression tests were given to them. To the experimental group, 24 sessions of under water psychomotricity activities were given. Afterwards, post-self expression tests were given to both groups to determine changes between groups. Data analyses were proceeded by SPSS 23. For tests of homogeneity, independent t-tests were administered and mean and standard deviation value of test items were calculated. In addition, paired sample t-tests were administered to search results of pre and post test. The significant level was set as .05 in every data. After administering of under water psychomotricity activities, results of this research were as follows: Self-expression increased after conducting aquatic psychological exercise program for adults with intellectual disabilities. In the subdomain, verbal self-expression, speech self-expression, and non-verbal self-expression increased.