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These cenotes are formed when limestone caves in. Some cenotes are part of a massive underground network of rivers and caves that remain, for the large part, unexplored.

The amount and variety of fish species on a coral reef can indicate the current condition and general health of a reef: plenty of herbivorous fish (eg: parrotfish) might suggest that algae cover on a reef will be kept under control (too much algae on a reef can smother corals causing major problems), the presence of large fish (including grey nurse sharks and groupers) might indicate that there are no issues with overfishing in the area, and a large variety of fish in a small area could indicate that the reef provides an important habitat for a range of fish species and is therefore a critical area to manage.