meow

eyes hit serious diminishing returns wrt resource costs vs vision quality as they get bigger, so the question became: what the FUCK do giant (and colossal) squid need to see so badly that they couldn't see with swordfish-sized eyes that's justifying that massive energy cost? that nothing else in the deep ocean needs to see so fucking badly??

turns out the one strength eyes that big really have over much smaller eyes is: seeing large glowing objects in water deeper than 500 meters from an appreciable distance.

sperm whales are the primary predator of giant squid. sperm whales don't glow. BUT! water that deep is full of bioluminescent creatures-- these creatures light up when bumped into. something a sperm whale's size is continuously bumping into those critters, it's just surrounded by a glowing field all the time when it's swimming at those depths, visible from a distance-- if you have the right eyes-- as a massive glowing shape. so basically the only reason to have eyes the size of soccer balls is if you live in the deep ocean and your life depends on having a heads up when a hungry sperm whale lurking around