Just because we can't see something doesn't mean it doesn't exist. This holds most true in physics, outer space, and in the oceans right here on planet Earth.
For instance, in 2015 researchers discovered a new species of seadragon, a type of fish related to the seahorse. After 150 years of scientists assuming there were only two species, the common and the leafy seadragons, further proof that ocean biodiversity has fewer bounds than we can even imagine was trawled up off the western coast of Australia — a male seadragon carrying a brood of babies. The individual was fire-engine red, but lacked the Las Vegas showgirl rack of feathery appendages associated with the other two known seadragon species.
Scientists initially thought they'd found a common seadragon (Phyllopteryx taeniolatus), even though it was caught at a depth of 160 feet (50 meters). That's unusually deep for that species, as most seadragons live in shallow kelp meadows 10-80 feet (3-25 meters) deep along the continent's southern coast. So tissues were sent off for genetic testing, which resulted in the revelation that for the past century, a third species of seadragon has been hiding in plain sight.
Thanks to new DNA sequencing technology, the ruby seadragon (Phyllopteryx dewysea) was scientifically described, but all that was known about it was its bright red color and that it likely occupied deeper waters than its relatives. Nothing about the animal's life cycle or habits could be proven, as it hadn't been caught in the act of doing ... well, anything. Until now.
New footage of two living ruby seadragons in action, chronicled in the journal Marine Biodiversity Records, has changed that. Caught on film by a remotely operated vehicle, the seadragons poke along like Don Quixote's horse through a dim, sandy-bottomed underwater landscape off the Australian coast. The area's dominated by sea sponges, and the seadragons curl and flex their prehensile tails. This is a feature that other seadragon species don't have, but which is probably necessary for the animals at this depth when seas get rough. No need for fancy plumes and appendages for camouflage in this sparse landscape, and though their red coloration might seem garish in full light, it probably helps the seadragons blend in deep below the ocean surface.
Of course, there's much more to be learned about this beautiful fish, like how and why it evolved a prehensile tail. This discovery's another good reminder that we have much to find in our planet's oceans.