What are the different types of defense mechanisms seen in marine animals?

Many marine animals have venomous spines. The puffer fish and urchin are two examples.

When puffer fish are in danger, they will puff up, making them appear more menacing and deterring predators from consuming them. If they are attacked while in this form, their poisonous spines will pierce the attacker and cause damage.

Similar strategies are employed by sea urchins, which have a robust hard shell covered in hundreds of venomous spines. This makes them difficult for predators to hunt, and it also causes problems when people trip over them. Because urchins are difficult to remove from the environment, urchin armies pose a threat to habitats, particularly "kelp forests," because they are difficult to stop due to their spines.

Some common defense mechanisms in marine animals include camouflage, mimicry, spines or armor, toxins, bioluminescence, and jet propulsion.