Most squid are completely harmless. I won’t even start with Giant squid or Colossal squid, because we know next to nothing about their predation style, and they live so deep in the ocean (>1.5 MILES down) that no human will ever encounter a healthy one. They pose no danger to people whatsoever.
But there is one other, very serious squid that can and has harmed people. The Humboldt squid (Dosidicas gigas) are a large species of squid native to Eastern regions of the Pacific Ocean near the Americas. These monsters are also known as Jumbo squid, Jumbo flying squid, Pota, and Red Devils. Sport fishermen catch them on rod and reel, and they are fished commercially in South America and Mexico.
Thankfully, they don’t typically come close enough to the shore to be dangerous to bathers, but out in the depths of the open ocean where these squid typically hunt, they are fearsome predators. These squid typically hunt in water at least 600 deep, but can be lured shallower, especially at night..
Counting the arms, these squid grow to nearly 6ft long (over 1.5 m) with their body alone being 3 ft/ 1 m. They are almost the size of a grown man. They are very active, aggressive predators with very capable brains. Just one Humboldt squid could easily ruin the day of a diver, but they typically hunt in packs, and have been observed using some clever teamwork tactics. Check this squid out:
That’s already a pretty scary squid, but consider this: instead of featuring regular ol’ suction cup suckers like most octopus and squid, they have something slightly more intimidating: suction cups lined with little saw blades. You read that right. Saw blades.
Made of the same material as cat’s claws, each sucker also features a very sharp toothy ridge that can dig into the flesh of it’s victim. Anything a Humboldt squid grabs is definitely staying grabbed.
Photo Credit: Dive Discovery
Hidden inside the ring of saw-tooth laden suckered arms lies the final weapon in the Red Devil’s arsenal. All cephalopods feature a beak in the middle of their arms, and the humboldt is no exception. The beak of a this squid can be as large as a tennis ball, and is a perfect tool for taking big bites out of its victim.
Photo credit: HA auctions (and OMG I can buy a big squid beak!!!!)
As a cherry on top of this whole experience, anyone witnessing a feeding frenzy of Humboldt squid will quickly realize where the Red Devil nickname came from.
Like many squid, it appears that these squid communicate with one another using a series of color flashes and sophisticated skin patterns. Scientists have observed and recorded many instances of these squid flashing color patterns to one another, but nobody has undertaken a dedicated study to figure out what they’re saying. one thing is very clear: when these squid attack, they flash bright red and white so quickly, they appear bright red.
With this answer, I have painted a sensational image of a squid that definitely can harm people if it wanted to, but the truth is we really don’t know a lot about their behavior. They can be very scary, and there are many outfits up and down the Pacific coast that offer caged nighttime squid dives just like shark cage expeditions. I’ve never been on one, but I’ve heard that the squid definitely deliver: whipped into a frenzy by chum in the water, these huge squid darting all over in the inky blackness of the night between spotlights, seizing huge pieces of bait fish with their toothy arms, fighting amongst themselves over the morsels and flashing an angry red hue the whole time. But scientists have recorded just as many instances where these giants have approached divers with more curiousity than aggression, and many researchers have swam with whole schools of Humboldts and emerged with nothing more than a camera full of photos and an even more enhanced sense of awe.
I certainly hope that we can learn more about Humboldt squid before the fisheries ramp up their industry to the point where populations are threatened. Humboldts are already being recorded in more northern waters where they were never observed before. Where these squid were never seen North of San Diego, now they are observed all the way up in the colder waters of Oregon. Maybe it’s a sign of climate change and warming waters, or maybe it’s a sign that these squid are moving into ecological niches that other populations once occupied. I hope that these amazing squid will inspire more research than fear.