Stonefish
Steer clear of the stonefish’s dorsal fin spines. This is what this underwater predator uses to inject its victims with a kind of toxin that can stop the heart of an adult human within 24 hours. Unfortunately, they look so much like a rock that they can easily blend in with their surroundings. So, an unsuspecting beachgoer might accidentally step on one and experience the stonefish’s painful delivery method. If injected, doctors recommend you apply water that’s been heated to 113 °F (45 °C) to slow down the effects of the venom and buy yourself some more time to get to a doctor.