There are swim instructors who specialize in children and adults who have special needs and/or are very afraid of the water. Both of my children ended up having to take lessons with such an instructor and she is a real miracle worker. I know she also has adult students. I would reach out to local places that have swim classes and ask if they have a special needs swim instructor. She started my kids in the shallow warm therapy pool to remove the temperature and depth issues. If you find the right place and instructor, they could do the same.