If I don't have a place to swim to, I'm unsafe. If I can't see through the water, I'm unsafe. My fear is more dangerous to me than deep water is. In order to learn to swim I'll have to do things I don't like. I'm only safe if I can stand up or hold onto the side.
Shallow water is as dangerous as deep water.
Deep water won't hold me up. The water is more powerful than I am. I need to be more physically fit than I am to learn to swim. The TSI method may work for others but it may not work for me. I don't trust myself in deep water.