Talk:Crabsquid/@comment-69.166.94.44-20160505013231/@comment-107.223.130.147-20160508042101

That's like asking why we have hearing if we have eyes to see with. Creatures use multiple senses to detect environment around them. We evolved on the surface in air environment, so we rely on hearing, seeing clear images, etc. Things in water adapted hearing to use echolocation, they developed "lateral lines" to detect electrical impuses from biologics through water, etc. The eyes, being evolved for depth, may not perceive things the way we do. They may detect different registers of light, like ultraviolent or polarized, in order for it to "see" things, and it may only detect variations in light, not distinct images. The echolocation would work like hearing in that it gives it an idea of things around it that the eyes may not see. It's a fictiitious creature, but we can use what we know about the biodiversity of creatures on our planet to project how these fake creatures may function.