In 2016, during a deepwater exploration of the seabed around the Mariana Trench using a remotely operated vehicle, researchers from the National Oceanic and Atmospheric Administration captured this amazing footage.&nbsp;It's a sea cucumber (<a href="https://en.m.wikipedia.org/wiki/Enypniastes">Enypniastes</a>), which moves about the ocean through the mesmerizing undulation of their body and anterior sail-like veil. Sea cucumbers&nbsp; are relatively small - they're about 5 to 9 inches in length, have bulbous bodies and some species are even bioluminescent.NOAA Ocean Exploration tweeted the video clip, saying that the footage was taken while exploring a volcanic caldera at 1.9 miles deep (3,000 meters) under the ocean in the Southern Marianas.#seacucumber #marineanimal #NOAA #deepwaterexploration #MarianaTrench #Marianas