The best one shown so far was the show "Equator" and the episode was on coral reefs.
The entire one hour show was 100% focused on hard and soft corals and reef fish. You name it and it was talked about in detail. It was shown on Discovery HD and I have it recored on my DVR but I don't have any equipment to DL it with.
A must see, goes into coral growth, color, feeding needs etc.