Which type of coral is considered the most troublesome to divers due to its stinging cells?

Fire corals are considered the most troublesome to divers primarily because they possess specialized stinging cells known as nematocysts, which can deliver painful stings upon contact. These stings can cause irritation, discomfort, and in some cases, allergic reactions or more severe responses depending on the individual's sensitivity.

While other types of corals like leather, soft, and brain corals do play significant roles in the ecosystem, they do not have the same level of potency regarding stinging capabilities. Leather and soft corals tend to be more flexible and lack hard, stinging structures, and brain corals, while having a hard structure, do not inflict stings like fire corals. Therefore, the unique characteristics of fire corals make them a primary concern for divers when it comes to avoiding painful encounters.