pyjama sharks are very cute and curl into a ball as a defense mechanism
(some other shysharks will do this but pyjama sharks are the cutest and you can fight me on that)
shark skin is pretty much made of teeth. (literally. their scales are closer to teeth than scales)
the teeth skin is protective but also the rippled/textured surface of the teeth-scales is way more efficient in fluid dynamics and has been studied to try to improve water transportation and etc.
shark skin feels like sandpaper because of this
goblin sharks are deep-sea sharks and look like relatively normal sharks until they bite things and their mouths extend out like flesh horror pacman
several shark species are bioluminescent!! cookie cutter sharks glow green. kitefin sharks are the biggest bioluminescent vertebrate known, and unlike a lot of other marine life, they don't use bioluminescent bacteria to glow - it appears to be part of their skin itself, but we still don't really know entirely how that works yet!
nurse shark teeth look like little decorative fans...
horn sharks have little venomous spikes in front of their dorsal fins! that's how they got their name
sharks used to be called sea dogs
the above still shows up in some names, like "houndsharks" or the porbeagle shark
sharks can sense electricity so well that they can sense the neurological activity in their prey
shark skeletons are made of cartilage
sharks do not have ribcages
hammerhead sharks can sense the direction a smell is coming from the same way humans can tell the direction of sound because their nostrils are so widely spaced
sharks lose their teeth all the time and more teeth just get shoved to the front - their teeth aren't connected to the jaw like in humans
this is why shark teeth are so common and are often sold as souvenirs
there's a type of shark called a cookie cutter shark that doesn't kill prey but instead takes circular bites out of (sometimes much larger) fish like a demented melon baller
if you touch a shark on the nose or (in some) flip it upside-down, it will go into a sort of "trance" and stop moving for about fifteen minutes
researchers use that to study them safely
some shark predators have also used this to prey on sharks
there's a type of shark called a wobbegong. they look vaguely like decorative rugs.
basking sharks look nightmarish but they're genuinely pretty harmless. like, don't antagonize them, because they're huge, but they only eat plankton.
whale sharks are enormous but so docile that some people have tried to ride them. but do not do this. it can hurt them (and you)
Some sharks, like the epaulette shark and horn shark, use their fins to "walk" along the sea floor. it looks about as funny as you'd expect
