The rather tacky KQED episode "Deep Look" features a hagfish, a virtually blind, jawless, finless, scaleless eel-like creature that has survived millions of years by using streams of natural slime to choke prey for food. . These slimes grow to enormous sizes and can fend off even the largest aquatic predators in their path.
"What keeps the boneless, jawless hagfish thriving after more than 300 million years? SLIME. The goop it exudes – a mix of mucus and special protein cells – expands to 10,000 times its original volume in less than half a second, clogging the gills of its competitors and predators, including sharks!"