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A translucent jellyfish swims above a textured ocean floor covered in dark, round formations, set against a dark background.

2026 Cook Islands ROV Exploration

Dive 13: Western Rarotonga

August 11, 2026

Location: Lat: -21.168350524°; Long: -159.908979692°
Dive Depth Range: 2,387-2,543 meters (1.5-1.6 miles)
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After several days of rough weather preventing dives, the team was able to deploy the remotely operated vehicles (ROVs) for Dive 13 of the 2026 Cook Islands ROV Exploration cruise. The dive took place on a small ridge about five miles offshore the western side of Rarotonga, starting at a depth of approximately 2,400 meters (1.5 miles). The location took advantage of partial protection of the island in what was still marginal sea conditions for operations. Upon reaching the seafloor, the ROV encountered lobate former lava flows. Further upslope, seafloor geology shifted to manganese-encrusted sediment sheets that might be ancient ashfall deposits. We observed the highest diversity of corals and sponges of any dive during the cruise and also encountered sea stars, crinoids, sponges, a few fish, and other invertebrates. Five rock samples were collected for further analysis and seven biological samples were collected, including a sea star, two brittlestars, sea stars, three different types of corals, a jellyfish, and a crinoid. A light-colored layer of clay-ooze coated most of the rocky substrate, much more than visible at many of our deeper dives during this cruise. Five water samples for environmental DNA and carbon isotope analyses were collected, and the fourth Argo float of the cruise was deployed shortly after recovery of the ROVs.

An underwater scene featuring a slender feather star with feathery appendages, set against a sandy ocean floor and dark rock formations.

This crinoid was observed perched on a bamboo coral during Dive 13 of the 2026 Cook Islands ROV Exploration cruise. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 829 KB).

Underwater scene of a rugged seafloor with dark volcanic rocks and a pale starfish in the foreground.

This sea star was seen clinging to a rock (broken lobate form of lava) during Dive 13 of the 2026 Cook Islands ROV Exploration cruise. The sea star, which belongs to the family Goniasteridae, may be a species new to science, so was collected for further study. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 808 KB).

A submersible vehicle rests on the ocean floor, illuminated by blue lights, with a tether extending to the surface in a dark underwater environment.

A top-down view of remotely operated vehicle (ROV) Deep Discoverer exploring the seafloor. Captured from ROV Seirios during Dive 13 of the 2026 Cook Islands ROV Exploration cruise. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 341 KB).

Close-up of a pale starfish with textured arms radiating outward against a dark ocean floor.

A close look at a brisingid sea star imaged while exploring off Rarotonga during Dive 13 of the 2026 Cook Islands ROV Exploration cruise. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 965 KB).

Underwater view of a rocky ocean floor with textured gray rocks, smooth boulders, and fragmented pieces, illuminated by dim light.

Ancient lava pillows (left) and ferro-manganese-encrusted rocksheets (right) seen during the latter part of Dive 13 of the 2026 Cook Islands ROV Exploration cruise. These sheets may be remnants of ashfall from ancient volcanic activity. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 1.1 MB).