Playing With Fire Underwater: Fire Coral Demystified

Playing With Fire Underwater: Fire Coral Demystified

Most scuba divers who have dived in tropical or sub-tropical reefs would have been cautioned about getting stung by the notorious fire coral and would have filed away this information as just one of the many things that can harm them underwater. However, we believe every swimmer and diver should better understand these beautiful underwater organisms before heading to open water, particularly because of their inconspicuous predatory nature.

So what is fire coral? Read on to find out more about these hybrid marine life forms and learn how to keep yourself safe from their painful stings.

Interesting Facts About Fire Corals

royal angelfish swimming near yellow fire coral

So what does a fire coral look like and what do they do? The facts below will help you avoid these organisms when you go snorkeling or diving.


Also known as “stinging coral” or “red sea coral,” fire corals belong to the Milleporina species. And contrary to popular belief, they aren’t a true coral at all. Fire corals are actually marine organisms that form colonies and are closely related to the jellyfish family and stinging anemones.

Physical Appearance

Belonging to the family of Milleporina with the scientific name of millepora, fire corals have “many pores,” which upon closer inspection look like long fine hairs that protrude from their skeleton. The hairs possess clusters of stinging cells (nematocysts) that it uses to capture and feed on prey.

fire coral nematocysts up close

Unfortunately, as rather polymorphic organisms, a fire coral can appear in several physical forms (heavily branched, plated, or encrusted). In fact, there are reportedly almost 50 varieties of fire corals, making it even harder to describe. But most of the time, fire corals have bright yellow-green and brown skeletal coverings fading to a whitish hue at the tips.


Fire corals are widely distributed in tropical and subtropical waters. They are primarily found in the Indian and Pacific Oceans, forming extensive outcrops on projecting parts of the reef where the tidal currents are strong. They are also abundant on upper reef slopes and in lagoons, and grow at depths of around 40 meters.

Predatory Behavior

If you haven’t guessed by now, the fire coral gets its name from its stings, which leave a burning sensation on the skin of the unwary diver that brushes against it.

Divers often mistake fire corals for seaweed or true corals and may brush against them or lean on them for support. Upon contact, the very small nematocysts on the corals’ hairs release toxins, while the sharp calcified exoskeleton cuts the divers’ skin, causing intense pain that could last anywhere from two days to up to two weeks depending on the duration of contact and number of nematocysts that hit the wound.

Fire Coral Sting Prevention & Treatment

fire coral up close

The best way to stay safe from fire coral stings is to avoid them altogether, but we wouldn’t advise you to stay out of the water. Instead, a good preventive method is to practice and master buoyancy control. This should help you avoid unnecessary contact with sharp, stinging, and fragile coral reefs.

Divers tend to wear full wetsuits and diving gloves to eliminate chances of getting scratched and stung by fire corals. But when you do get into contact with them, particularly during warmer dives in your swimsuit or shorty, it’s quite easy to treat your own stings.

Because fire corals have tiny, stinging nematocysts—the same kind of cells that you’ll find on both poisonous and harmless species of jellyfish—step-by-step treatment for fire coral rash is similar to how you would treat a jellyfish sting:

  • Rinse the wound or affected area with salt water, as fresh water will increase the pain.
  • Use vinegar (acetic acid) or Isopropyl Alcohol to kill any remaining stinging cells clinging to your skin and help break down the toxin.
  • Use tweezers to put out any stinging hairs.
  • Immobilize the affected limb to prevent spreading.
  • Apply hydrocortisone cream as necessary to reduce inflammation. It is also critical to watch the wound for infection, which will have to be treated with antibiotics by a doctor.

If the diver displays signs of an allergic reaction, like shortness of breath and swelling of the tongue, neck, and face, he or she should immediately seek medical care.


  1. Reminds me of that Indiana Jones movie where his little assistant, Short-Round, steps on something, gets into trouble and afterwords says, “I step where you step! I touch NOTHING!!!”

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