This long-spined sea urchin at Hammerhead Gulch was one of very few among the Exuma reefs.

Years ago there was a mysterious die-off of these once-ubiquitous echinoderms throughout the Caribbean and Bahamas. The Bahamas were hit particularly hard. They have not yet fully recovered.

Ironically, this may be one of the reasons that visibility was poor. Sea urchins feed on algae. It could be that the lack of urchins is allowing the fleshy algae to out-compete the coralline algae necessary to reef building. The result is that the fleshy algae multiply and cover the reef. Then, even a minor storm can toss them into the water column, muddying the waters, as it were.