At 785 meters (2,575 feet) depth, remotely operated vehicle Deep Discoverer encountered a World War II-period causeway called a “rhino barge.” Rhino barges were large floating platforms comprised of joined-together steel pontoons that could transport vehicles and supplies to beaches. This is one pontoon.

At 785 meters (2,575 feet) depth, remotely operated vehicle Deep Discoverer encountered a World War II-period causeway called a “rhino barge.” Rhino barges were large floating platforms comprised of joined-together steel pontoons that could transport vehicles and supplies to beaches. This is one pontoon. Image courtesy of the NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts. Download larger version (jpg, 1.6 MB).

An unusual observation of a six gilled stingray, Hexatrygon bickelli. Although these animals are found across the Pacific, scientists know almost nothing about the biology of this species. Found at approximately 835 meters of depth, this could be the first live sighting of this animal.

An unusual observation of a six-gilled stingray, Hexatrygon bickelli. Although these animals are found across the Pacific, scientists know almost nothing about the biology of this species. Found at approximately 835 meters (2,740 feet) of depth, this could be the first live sighting of this animal. Image courtesy of the NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts. Download larger version (jpg, 1.1 MB).

Dive 21: “Caiman” Anomaly
September 28, 2017
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Dive 21: Finding Mysteries

Dive into the mysteries of the deep! While exploring at a depth of ~800 meters (2,625 feet) off of Hawaii, the team caught glimpses of a rare six gill stingray (Hexatrygon bickelli) as well as a lantern shark. Video courtesy of the NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts. Download (mp4, 34.7 MB)

An important, and exciting, part of exploration is investigating sonar anomalies – we are never certain what will be found! Sometimes these anomalies reveal rocks, other times they show us a glimpse into our cultural heritage by revealing wreckage from years before. The “Caiman” anomaly was identified in multibeam data from early in the Deep-Sea Symphony expedition. The objective for this dive was to complete a characterization of the sonar anomaly and – if the anomaly was a cultural heritage target – confirm its identity, record its condition, and document damage from its disposal or sinking. It was thought that the anomaly could be the remains of a Japanese fast submarine I-203 (Sentaka-type) that was captured at the end of World War II and brought to Pearl Harbor as part of a five-submarine prize fleet. These submarines had been disposed of near this area in 1946, so it was certainly possible. Five waypoints were selected from the multibeam sonar targets. However, when all five waypoints were examined by the remotely operated vehicle, they were found instead to be geologic formations of basalt rock. The I-203 Japanese fast submarine was not located. There was an unexpected target identified: the remains of a World War II-period floating causeway, otherwise known as a “rhino barge.” Some of the biology highlights included a large conger eel, cusk eel, anglerfish, scorpionfish, rattail, a six-gilled stingray, crab, sea star, crinoids, urchin, bivalves, anemone, precious coral, cup coral, stony coral, jellyfish, and glass sponges.