I answered this question a long time ago. My daughter was considerably younger, but to this day at almost 18, she still is NOT all that comfortable in the water. Never in a million years would I do it again. Here is my original response.
We did this course with our oldest daughter 15 years ago, and I can truthfully say that I would never do it again. It instilled a fear of water/swimming with her. It took two years of semi-private lessons in a warm, loving, and nurturing environment to help her overcome her fear. At 17, she is still not a great swimmer and is really hesitant to get in deep water. We started our younger daughter in mommy/tot lessons at 9 months old. She learned many of the same things as ISR but in the warm, loving, and nurturing environment. She also learned to swim not just survival swimming. She took lessons for 9 months. She loves the water to this day. During a homeschool period in 5th grade, we enrolled her in lessons at the rec center in a neighboring community. Mind you she had not taken lessons since she was 18 months old. She was placed in level 2, tested out of that, placed in level 3, and tested out of that. She completed level 4 and 5 and is a beautiful and strong swimmer. We don't live near the water and the closest pool is 20+ miles away, so she doesn't have the opportunity to swim on a regular basis, but the skills are there. I do believe that swimming is a life skill and learning to swim is not an optional choice. I just believe that ISR is not the right choice and would never choose to expose my child to this harsh method again.