Learning to swim enables children with developmental disabilities to acquire motor and functional abilities as well as new acquaintances and friends that are essential for increasing their quality of life. The primary goal of training non swimmers with developmental disabilities is to train them to independently swim twenty-five meters and thus ensure a safe stay in water and the environment where water is present. The aim of the research is to show how much swimming lessons contribute to motor development and abilities in the water in non-swimmers with developmental disabilities. Based on the comparison of the results of two consecutive training programs for non-swimmers according to the Halliwick concept and the assessment of swimming knowledge, we will find out the level of progress achieved by the children, i.e. whether the progress achieved differs among children with different developmental disabilities. A conclusion will be drawn on the effectiveness and importance of regular implementation of the program. The sample consists of ten participants of the training program for non-swimmers "Hrvatska pliva" in 2020 and ten participants of the same program in 2021. The attendees are children with various disabilities (autism, Down's syndrome, physical impairment, cerebral palsy). The two examined groups differ with regard to the representation of the type of disability within each group. With statistical calculation using Mann Whitney U test, the results of the research showed that there are no statistically significant differences between the two groups of non-swimmers with developmental difficulties in the field of swimming knowledge and Halliwick assessment variables.