I have posted this before I am sure. I noticed most of the Olympic swimmers did use the slightly opened finger concept. I have been teaching the open finger concept for over twenty years, the reason less tension in the forearm. The way to check this is to hold the fingers together and press the thumb against the index finger. You will feel the tension in the forearm. Then relax the hand without pressing the thumb against the index finger and allow the fingers to seperate the tension in the forearm disappears. Forearm tension is what causes shoulder problems