Scuba Diving Touch Me Nots (Part 2)

Often mistaken for harmless plants or nonliving gelatinous masses, marine invertebrates and coral can cause allergic reactions, stings and often contain toxic venomous substances that can cause severe injury to divers if encountered. We have listed a few such hazardous creatures, which can cause to serious harm to unaware or inattentive divers through contact.  Essentially underwater contact irritants consist of any substance that when the skin comes in contact with a substance that acts as an irritant and causes contact dermatitis. This is the second part of our two part series on Scuba Diving touch-me-nots. If you missed the first part Click Here.

Sea Cucumber

Sea Cucumbers

Though Sea Cucumbers are seemingly harmless, when under threat, these animals will expel  holothurin which is a white sticky like substance from their Cuvierian organ.Holothurin is a strong poison and the venom of the sea cucumbers quickly weakens the muscles of the enemy. Sea Cucumber venom is toxic to humans if the Cuvierian tubules come into contact with the eyes, the result may be permanent blindness.

branched firecoral

Fire Coral

Fire Coral also known as Stinging or Red Sea Coral belongs to the Milleporina order of species and contrary to popular belief isn’t really a coral at all. Fire corals are marine organisms that form colonies that look just like real coral; they are actually closely related to the jellyfish family and other stinging anemones.   The Fire Coral gets its name from the painful burning sting that it inflicts on the unwary diver that brushes against it. A fire Coral sting can cause intense pain and can be felt from two days to up to two weeks. (Also Read: Playing With Fire Underwater: Fire Coral Demystified)

crown of thorns

Crown-of-Thorns Starfish

Out of all starfish species, the Crown-of-thorns starfish is probably the most dangerous to divers. The sharp spines on the sides of the starfish’s limbs resemble thorns and create a crown-like shape, giving the creature its name. These thorns are very sharp and are capable of piercing through wetsuits and other clothing and are contain a neurotoxin that can cause onset of edema, erythema ,pain, as well as nausea and vomiting. Crown-of-thorn starfish are found in  tropical coral reefs in the Red Sea, the Indian Ocean, and the Pacific Ocean.



Hydroids are feathery plants like creatures closely related to jellyfish, with stinging cells, and are sometimes referred to as fireweed. Hydroids are actually colonies of animals equipped with strong stinging cells (nematocysts) used to capture prey and for defense. Attached to virtually any firm surface including rocks, seaweeds, and man-made objects including docks and mooring lines Hydroids are one of the primary causes of itching and skin irritation for divers that accidentally come in contact with this tiny creatures.  Two species to avoid in particular are the white, fine feathery ones known as the Feather Hydroid  and the denser yellow/brown variety.


Sea Urchins

Divers are especially wary of these creatures mainly due to the fact that accidental stings while walking in a shallow reef, or touching one accidentally while Scuba diving can be a painful proposition. The spines of sea urchins remain in the wound making wound heal slowly. Sea urchins inject a small amount of venom when stinging, but the amount is negligible to cause any serious injury , around 10 species of Urchins are poisonous but there are a few that are deadly. Sea urchin stings must be washed thoroughly and rinsed with vinegar to wash out the stings and then watched over the next couple of days for signs of infection. Divers should be constantly vigilant where they place their hands, to avoid an accidental encounter with these spiny devils.

* Photo credits: photos by Nemo’s Great Uncle, jon hanson, enje, Dungodung on flickr

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