I think it might describe a group of squid feeding. Which makes the "turmoil" part even more apt. I don't know if they travel in schools, but the thought of traveling squid doesn't conjure "turmoil" as much as their behavior when feeding does. I think they travel pretty smoothly, like torpedoes.
Not that I would know. I don't hang out with squid too often. I would like to, though. They seem nice.
I saw a show about that, mollusque. I think it was Nova, actually. They followed a biologist who was trying to find out if Humboldt squid really are vicious--there's no doubt some have attacked fishermen (let's be frank--squid-jiggers) who have fallen in. But this biologist wanted to know, where these squid upset and angry and aggressive only in fishing areas? Because outside of those places, when they're not being "attacked" (from their perspective) by humans trying to catch them, they are quite peaceful. It was a remarkable show. I highly recommend it.