I went with an outfit called Seasir. They pick you up in the morning at your Naha hotel. I had signed up for their Kerama Island excursion, but was disappointed when they made the decision on the fly that they would change course and go instead to an area just offshore from American Village. It was a sunny day but I guess they saw something in the forecast they didn’t like. Other than that, they were fine. Well organized.
Near the main island, Kerama is where you want to go.
I think I may have been the only person on the tour in their 40’s. Most were probably in their 20’s, some 30’s.