Dangerous marine life includes various species that can pose threats to humans. For example, the box jellyfish is known for its potent venom, which can cause severe pain and even death. Other dangerous creatures include stonefish, which have venomous spines, and blue-ringed octopuses, whose bite can lead to paralysis. Additionally, some sharks, like the great white shark, are often feared due to their size and predatory nature. While attacks are rare, they can be serious. It's essential to be aware of these creatures when swimming or diving in oceans to ensure safety and avoid encounters.