This thing looks like a stone. Now, there are two things that you need to know about this fish. First, if you confuse it with a rock and steps on its spikes, it will poison you, and you will lose your leg. The stonefish is very economical. It injects the amount of poison proportional to the pressing weight. The second thing is it takes the stonefish just 0.15 seconds to react to a moving object (another fish or your leg) to opens its mouth and bite it that is why losing a leg is possible. So, watch your step when you are in the ocean.