One of our family's big achievements in our early years with special needs and autism was teaching both boys, #2 with classic autism (now "Aspergers") and #1 with more complex disabilities, to swim.
This took years of persistence and patience, fueled by Emily's hatred of preventable drowning. Try and fail. Try and fail. Pool one and two. Teacher five and six. Again and again. Money spent and lost - more than many could afford. Private and group. Family practice.
After years of this they could swim enough. After that it was improvement. #1, if he were motivated, could be competitive in butterfly -- a stroke I can't do. (I'm a strong swimmer.)
#2 just passed his "pre-lifeguard" course.
You never know.