What are squids defenses?

It's main mechanism of defense is intimidation. Using bioluminescent sacs on their bodies, they light up and it scares the predator away. Another method, when intimidation doesn't work, a large oval lights up, facing the anterior end of the predator. As it swims away, it also closes the tissue around the oval, making it appear smaller. This creates the effect that the squid is very quickly escaping, and the predator gives up.