More accurately, paddling with oarfish! Participants on a recent Shedd Adventures expedition had the unexpected and rare treat to witness live “sea monsters” in the shallow waters of Baja California. The YouTube video of the surprise encounter, above, had more than 2 million views at last count.

Thought to be among the origins of sea serpent tales, the oarfish (Regalecus glesne) is the longest bony fish in the world, reaching a length of 36 feet, and quite heavy at nearly 600 pounds. Rarely seen by humans, when oarfish are found in the shallows, they are usually dead or dying. Previous theories have even linked their nearshore appearances to impending earthquakes, but those ideas have generally been abandoned by scientists. Oarfish do, however, tend to swim ashore in pairs, as seen here, but reasons for this are still unknown.

Oarfish have an attention-grabbing appearance. The dorsal fin runs the length of the body, with reddish rooster-like projections sprouting from the first dozen fin rays near the top of the head. Long pelvic fins help them stabilize in a “heads-up” vertical orientation in their preferred depth of close to 1,600 feet. This vertical stance is believed to help them locate prey—krill, small fishes and squid—by their silhouette against surface light.

Study of their deep-sea swimming (by the SERPENT project, 2008-2011) also indicates they can just as easily move backward as forward, called “palindromic” swimming, which we see in fishes like eels. As seen in the video, oarfish swim by undulating the long dorsal fin, called amiiform swimming (named after the somewhat more familiar but still bizarre bowfin Amia calva).

Little is known about the ecology of oarfish, although this body of knowledge continues to grow thanks to ongoing research, including studies of two dead specimens that were found nearshore in 2013. Analyses of their internal parasites and anatomy shed light on their place in the deep-sea food web, as well as reproductive characteristics.

From the deep sea to the shallows, sea serpents are mythical creatures, but the oarfish shows us there are still many fascinating mysteries to uncover about the ocean and its inhabitants.

Solomon David, postdoctoral research associate

With Shedd experts as your guides, the Shedd Adventures travel program takes you beyond the usual destinations to get close to wildlife in wild places—where astonishing experiences like the oarfish encounter can happen. Check out our remaining 2014 expeditions and the list of trips coming up in 2015.

For more information about Shedd Adventures, contact Cheryl Mell at cmell@sheddaquarium.org.

The video footage is provided by Un-Cruise Adventures and was shot by Wendy Keaton and an Un-Cruise Adventures guide.