By holding on to heavy things that won't move, like rocks.
Yes, sea stars are able to move the spines in order to protect themselves as armor.
They try to camouflage themselves.
they protect themselves by rolling into their 5 sided column rolling ball and they spit up a type of poisoning called pussitoligus
A sea urchin's body is covered in sharp spines.
They have to protect themselves from sea otters and birds
Having pointy spikes to protect themselves.
enimies
they use it to disguise themselves
It lodges itsef into holes or crevases
they protect themselves from larger carnivorous fish by hiding among the tentacles of Sea Anemones- which would sting and eat the larger fish... The Clown fish is immune to the Sea Anemone's stings.
Sea walls work by acting as deflectors which help to break the force of incoming waves. The power of the waves is weakened before they make landfall and, by reducing the force of the sea in this way, sea walls help to protect the beaches, cliffs and harbours from erosion.
Sea spiders protect themselves by being very agile and flexible, allowing them to escape predators quickly. They also have sharp claws that help them grip onto surfaces and defend themselves if needed. Additionally, some species have toxic venom to deter predators.