If you see a hagfish don’t anger it. Under attack, these bottom scavengers and hunters releases thick, clear slime in astonishing quantities. Potential predators back off quickly when presented with the slime, because it clogs their gills. The hagfish itself escape their own mucus that they tie their bodies into a knot and scrape it off (A highway in Oregon was harder to clean up after a truck full of hagfish crashed there last year.)
However, it turns out that this mucus is a precious resource for a hagfish. After sliming a predator, the fish can take nearly a month to refill its slime glands. So leave the poor slime monsters alone.
Read about it here.