A protected back reef?

For me it’s very surprising since this is my first time saw a coral zonation in this area. This area lies in Gunung kidul area which well known with its high wave action. In term of ecology, wave action is one of limiting factor for coral growth. Anyway, the “sheltered moat” nearshore behind rock structure usually called a protected back reef which provides protection from strong wave exposure and usually make coral larvae easier to settle. Interesting!