This 27 December 2018 video from the USA says about itself:
Tomopteris deep-sea worms
Tomopterids are pelagic polychaete (segmented worm) with paddle-like parapodia that propel them through the water column. They are relatively common in the deep mesopelagic, or twilight zone, and can live down to about 2,500 meters (8,200 feet).
Many Tomopterids are only a centimeter or two long, but some can also get to be quite large—up to 30 centimeters (12 inches!). They are voracious predators, using their speed and agility to capture and consume a variety of midwater organisms. Tomopterids are one of a few organisms observed spewing yellow bioluminescent mucus, presumably to deter predators. Yellow bioluminescence is rare in the deep and scientist don’t yet know why this worm has adapted this ability.