Parastichopus parvimensis

P. parvimensis (Warty sea cucumber) larva tracked using Gravity Machine showing an upward, helical swimming trajectory, but don't be fooled, if you watch to the end of this data-snippet, around time-stamp: 126 s, you see the larva transition to a new behavioral mode wherein it ceases upwards swimming and generates a strong feeding current which allows it to also hover in the water column.