Eels

There are well over 100 species of Moray Eels around the world, ranging in size when adults from a mere 30cm to an impressive 240cm. Most of the different species have quite a distinctive colouring consisting of stripes, spots or intricate patterns, so each type is quite easily identified.

Here on Koh Tao, we get multitudes of moray eels and they can be seen at practically every dive site. One of the most common here is the White Eyed Moray Eel - Siderea thrysoidea. They are one of the smaller of the species normally being around 40cm long though can grow up to 65cm.

Generally they have a pale yellow-brown body with a dense scattering of small brown spots with a purplish grey head with the eyes being its distinguishing feature as the iris is always white hence the name.


We also see the Yellow Edged Moray - Gymnothorax flavimarginatus. They can grow up to 120cm and are generally a yellow-brown colour  with the dark spots along the body and head. They also have a black patch on the gill opening and normally have a dark coloured iris.


Occasionally, we are lucky enough to see a Giant Moray - Gymnothorax javanicus. These beasts are the largest moray in the region and can grow up to 240cm and can weigh over 36kg!

While juveniles are light brown with large black spots, adults have black specks that grade into leopard-like spots behind the head and a black area surrounding the gill opening. Also in old giant morays the head is actually over-proportionally large compared to the rest of the body.


All morays have a fairly, muscular compressed body with a thick tough skin. They have a dorsal fin which runs almost the entire length of the body, from the head to around the tail and anal fins and are made to appear like a snake by their absence of pectoral and pelvic fins. Their head is large with small eyes and a wide mouth with teeth size depending on their type. They also have a secondary set or toothed jaws in their throat called pharyngeal jaws, which are thrust forward to grab and drag prey down through their digestive system. They are the only known creature to use pharyngeal jaws to grab and hold prey.

They have gill openings reduced to a small hole that is located mid-laterally behind the head. Due to the small size of these gills, morays have to continuously open and close their mouths in a gaping fashion to maintain a flow of water and facilitate respiration.


Probably more divers are bitten by morays than by all other sea creatures added together-usually by putting their hands into holes to collect shells or removing other items. If a moray does bite it often refuses to let go, so unless you can persuade it to with your knife, you can make the wound worse by tearing your flesh as you pull the eel off. If you do get bitten then make sure it is thoroughly cleaned, then seek medical advice as you may need stitches, tetanus and antibiotics as the bites practically always go septic. Saying that though, Morays are in no means aggressive creatures and most have relatively poor eyesight and rely on their sense of smell, often coming towards divers just to investigate. They won’t jump out and bite you so as long as you don’t stick your hands down any holes or try to grab hold of them you’re fairly safe! A lot of the time you will see the Moray Eel half hidden in a hole, though if you’re lucky you will catch them swimming along the reef. Either way they make a good photo opportunity, often stopping to pose for you!