This stunningly beautiful jellyfish was seen during Dive 4 of the 2016 Deepwater Exploration of the Marianas expedition on April 24, 2016, while exploring Enigma Seamount at a depth of ~3,700 meters.
Scientists identified this hydromedusa as belonging to the genus Crossota. Note the two sets of tentacles — short and long. At the beginning of the video, you'll see that the long tentacles are even and extended outward and the bell is motionless. This suggests an ambush predation mode. Within the bell, the radial canals in red are connecting points for what looks like the gonads in bright yellow.
Video courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas.
Learn more about the expedition here: http://oceanexplorer.noaa.gov/okeanos/explorations/ex1605/welcome.html