I assume that my DS had a frightening experience during a YMCA swimming lesson when he was 3. He has never spoken of it and the teachers never saw what happened. But one day he just refused to go in the water and sat on the side of the pool. His fear prevented him from swimming for several years.
When DS was about 8, we found a college student who gave private swim lessons in her parent's pool over the summer. She was working on her PE teaching degree with special ed endorsement and she was a Godsend for DS. She was amazingly patient. Her prices were quite reasonable. After 3 summers of lessons DS is now a competent swimmer with little water anxiety.
From watching DS, I do think there were sensory issues involved. It was the feel of water in his nose that really freaked him out. When he did get his face in the water, he would take about 5 minutes at the side of the pool, meticulously clearing our each nostril. Once he felt better, he would have a minute of lesson and another 5 of clearing out. But each lesson got a bit better until now he is diving of the diving board and swimming under water the length of the pool.
As my Spanish speaking friends say, "Poco a poco." little by little.
