length
Explanation
The comic shows a sea cucumber watching a video on a laptop. The video features another sea cucumber making a provocative claim: "Oh, females SAY they don't care about size and length but you KNOW if they don't see you ejecting your viscera at least six feet they are looking for the next guy." The caption reads: "Sea Cucumber Youtube is about the same as human Youtube."
The joke relies on knowledge of real sea cucumber biology. Sea cucumbers have a famous defense mechanism called evisceration, in which they expel their internal organs (viscera) through their anus to entangle or distract predators. The comic transposes the format of toxic, insecure male content creators on YouTube -- who obsess over body measurements and make dubious claims about what women "really" want -- onto the animal kingdom. The "size and length" bravado that is a staple of human male insecurity content becomes, for sea cucumbers, competitive bragging about how far they can eject their guts.
The humor comes from the structural parallel: the rhetorical style, the laptop, and the "BUY NOW" advertisement are all perfectly recognizable tropes from human social media, but the specific subject matter is grotesquely biological. The caption drives the point home by noting that the two versions of YouTube are essentially interchangeable, implying that human male posturing online is not much more sophisticated than a sea cucumber measuring its viscera-ejection distance.