My friend and colleague Stephalopod published this cool paper a couple of years ago about how deep-sea squids use their ink. The fun fact from this paper that I trot out most often in social situations is a weird behavior called "mantle fills."

Six ink release types were observed: pseudomorphs, pseudomorph series,
ink ropes, clouds/smokescreens, diffuse puffs and mantle fills.

Most of these behaviors make some sense. Pseudomorphs, for example, are coherent, vaguely squid-shaped blobs of ink and mucus, left behind as decoys while the squid jets to safety. Smokescreens are self-explanatory. However,

The function of ink ropes and mantle fills is unknown.

A "mantle fill" is just what it sounds like--the squid fills its mantle with ink, and holds it there. When I explained this to a friend tonight, he said, "They wet themselves? That's so sad!"

Heh. Maybe that's all it is. But it's a pretty stereotyped behavior and there's probably something deeper going on. I eagerly await Steph's next paper!