This is by far the most poisonous fish in the world. It is particularly dangerous to people because, lying on the ocean floor, it looks just like a rock - or a stone. However, because the Stonefish is also food to other animals, it has developed a row of 13 poisonous spines down its back as a defence mechanism. Each spine is surrounded by a sheath, which holds the poison glands. When an unlucky human steps on a Stonefish, the spine penetrates the foot, the sheath is pushed back and the poison glands squeezed until they shoot their venom along grooves in the spine - deep inside the victim.
Medical help is absolutely essential.
When in danger, a stingray will lash out with this tail with great force. This can cause serious cuts, even requiring stitches. As well as this, many stingrays are also poisonous. People wading are most likely to be affected - although the stingray doesn't actually 'attack', it will lash out if frightened or if it feels trapped. If you shuffle your feet, splash and make plenty of noise, most stingrays will quietly disappear long before you get there.