1. Venomous
Out of the list of animals assigned the following animals have evolved to be venomous for the main reasons of protecting and feeding themselves.

Octopus
The octopus has paralyzing saliva which it uses in catching its prey. The saliva is injected into the prey, which then softens the flesh of the prey making it possible for it to be eaten by the octopus.

Yellow Bellied sea snake

Yellow bellied sea snake is also highly venomous and it chews poison into fish and then swallows them. These snakes use their neurotoxic venom against their fish prey. They inject deadly venom through non-movable hollow fangs located at the front of their mouth to immobilize its prey. Even a small amount of their neurotoxic venom can cause death. This has allowed it to hunt and feed itself.

The Man o’ war

The Portuguese man o’ war also has tendrils that are covered in venom-filled nematocysts used to paralyze and kill fish and other small creatures. Muscles in the tentacles draw prey up to a polyp containing the gastrozooids or digestive organisms.

2. Color Complexion

Animals have different skin colors that serve many purposes. At times they guard the animal from danger by camouflaging it from the view of a possible hunter where at times it severs as a warning to other animals that keeps them from approaching the specific animal.

Anglerfish

The Anglerfish is able to blend into the darkness because of its dark grey and brown color. Therefore, it is able to hide itself from possible predators.

Starfish

Many starfish wear striking colors that camouflage them or scare off potential attackers. They use color, pattern and texture to camouflage on sand, coral, rocks and the ocean floor. Some starfish also have the ability to change colors to camouflage themselves from other enemies.

Octopus

The octopus has smooth skins and special pigment cells that allow it to change color to blend in with the environment. Octopuses also adapt the texture of their skin and their body posture to blend in flawlessly with their environment
Moreover, the areas around the eyes, suckers, arms, and web may darken so the octopus appears more threatening. Their coloration also reflects their mood. Their pigmentation is usually brown; however, octopuses may turn white, which shows fear, or red, which demonstrates anger. Therefore, color completion acts safety mechanism for the octopus.

Yellowbellied snake

Yellow bellied snake is dark brown or black in color with a bright yellow or pale yellow underside which extends up the sides. These colors make it appear threatening to other animals which prevent them from attacking the yellow bellied snake.

Leather back turtle

The cover of the leather back turtle is dark grey or black with white or pale spots. These colors allow it be camouflaged.

King penguin

These animals are dark on the back surface and white on the underside surface. The dark back side blends in with the dark ocean depths when viewed from above. The light front side blends in with the lighter surface of the sea when viewed from below. The result is that predators or prey do not see a difference between penguin and the environment making it easier for the king penguin to hunt and to protect itself.

Whitei's seahorse

The coloring can change from a pale almost transparent, to a brownish black, and some can even be yellow. These colors allow these animals to blend in with the environment and they are often colored as the habitat they living in. This color patterns is used as a protection from predators, as a camouflage tool when searching for food, as well as a greeting gesture.

Hammerhead Shark

They are gray-brown to olive-green on top with off-white undersides. These colors camouflage them when they are hunting as looking from the bottom the off white color blends with the surroundings and makes it hard for its prey to spot this predator.

3. Sensory body parts

Hammerhead shark

These animals have unique sensing ability, especially in its head area. It can detect the electrical fields created by prey animals. This allows it to find its prey including its favorite meal, stingrays, which usually bury themselves under the sand.

Angler Fish

The male Angler fish has a sensitive olfactory organ that helps detect the female. Therefore, this helps the angler fish in their reproduction.

4. Body shape

Flattened body

Some organisms have flattened bodies which allow them manure fast in the water.

Yellow bellied sea snake

The Yellow bellied sea snake has a flattened body and the tail is even more so flattened to facilitate swimming. It also has a laterally compressed tail, which acts as a paddle. It can move quickly and all these characteristics enhance its ability to hunt more efficiently

Manta Ray

This creature has flattened flukes for bodies, broader than long, which allows it to swim faster.

Laterally compressed

The laterally compressed body shape of these organisms also allows them to maneuver faster in water making it harder for their prey to catch them. Both Angler fish and the Sargassum Fish exhibit these adaptations giving them the aforementioned advantages.

5. Regenerate body parts

Starfish

The starfish has the ability to regenerating arms that were lost to predators. This division of the body may happen involuntarily due to a predator or it may be actively shed by the starfish to escape. The loss of parts of the body in response to a predator is achieved by the rapid softening of a special type of connective tissue in response to nervous signals. Therefore, this special adaptation allows the star fish to escape its predators and also to ensure its survival.

Octopus

The octopus also has the useful ability to regenerate a tentacle if it loses one.