Science in Submarines

by Danielle Schimmenti

Welcome on board!

In the fall of 2017, during my first semester of graduate school, I joined the science team aboard the University of Hawaii’s R/V Ka’imikai-O-Kanaloa for a deep-sea submersible diving cruise. During the course of my 30 days at sea, we traveled to several seamounts (former islands now sunken beneath the ocean’s surface) in the Pacific. There we sent manned submersible vehicles to the ocean floor to do surveys of the overall health of the deep-sea coral reefs found there, as well as to collect some very rare live and fossil (dead) coral samples. I cannot reveal the names of the sites we visited or the exact nature of what we observed during our dives as this project is still ongoing, but I’d like to share a bit of what it was like doing research using submersible vehicles.

Me standing between the Pisces V (left, yellow) and Pisces IV (right, white) submersibles on the dock at the University of Hawaii Marine Center in Honolulu Harbor.

What is a submersible vehicle?

A submersible vehicle is a small submarine. Manned submersibles or human occupied submersible vehicles (HOVs), such as the ones used on my cruise, hold at most three people and can dive to 2,000 meters below the sea surface. HOVs are generally used for any oceanographic research that would require diving deeper than 300 meters (the maximum limit for scuba diving) below the water surface for direct human observation.  We carried two HOVs aboard our cruise, the Hawaii Undersea Research Laboratory’s (HURL) Pisces IV and Pisces V, and deployed both at every site we dived on.

Dive days

Each sub was manned with three people - one pilot, a PI/Chief Scientist, and one other member of the science team each; so, each of the six students on our team would get to dive about once every other week. If it was a dive day and you were scheduled to dive, you would be up early in order to prep for the long day ahead. This included getting dressed, packing a bag of warm clothes and socks and snacks, and eating a small breakfast. Each dive lasted up to 8 hours with no bathroom and no heat (the deep ocean is cold y’all). By 8:15 am you would be waiting in the hangar on the back deck of the ship where that day’s divers would be called to board their respective subs and be sealed inside. Then, one after the other, (Pisces V always first, Pisces IV second) each sub would be slowly and carefully hoisted off the deck and into the water where it would descend into the deep blue.

View of Pisces IV getting ready for deployment from the hangar (left). Pisces V being hooked to the winch used to hoist it off the ship by a HURL team member (middle). HURL team members approach Pisces IV in the chase boat to attach the tether line of the winch so the sub can be recovered out of the water and back onto the ship’s back deck (right).

Inside the sub

Being inside the sub was like sitting inside a small metal sphere. There were cushioned benches in a U-shape along one half of the hull, opposite the three portholes that allowed a view of the ocean floor in front of us. The pilot would kneel at the center of the “U” to man the controls, and the two observers (science team members) would sit on either side of the pilot. To get the best view through the porthole you had to lay on the cushioned bench on your belly. The hull was tall enough (~6 ft tall, ~1.8 m) that one person could stand at a time if ever needed, but mostly, we all alternated between sitting up and laying down over the course of 8 hours. Life support was necessary inside the sub because being deep below the ocean surface meant there was no source of fresh air. We supplied oxygen to our little metal sphere via oxygen tanks and removed the carbon dioxide we respired using scrubbers equipped with canisters of soda lime. The subs each carried enough life support to last three days. It was the job of the observers to monitor these systems during dives, changing the soda lime canisters every few hours.

Me laying on the observer's bench inside the
Pisces IV submersible
Science in the deep

Once the sub reached the ocean floor, we first had to obtain coordinates of our position via sonar radio from the tracking team aboard the ship. These coordinates were used to plan our routes (i.e. transects) to investigate deep sea corals. Transecting involved travelling at a constant speed for a set distance along a specific depth contour of the seamount - the goal being to transect all depth contours on all sides of the seamount for every site we visited. All transects were recorded on video via underwater cameras mounted on the front of the sub. This footage would later be used to categorize the nature of the terrain along the different depths as well as profile how the deep-sea coral reef on each seamount changed with depth in terms of observable species richness, diversity, and overall health. Once transects were complete we would often return to specific locations we had passed during our transects in order to collect living or fossil samples of coral. The samples were collected using robotic arms, and placed into baskets attached to the front of the sub.

Returning to the surface and post-dive duties

Once transects and sample collections were complete, the dive was over. At this point the pilot would radio up to the tracking team to confirm the sub’s return. Thirty minutes later the sub would reach the surface and be recovered out of the water onto the deck. Finally, the people inside could de-board. After being stuck in the vessel for 8 hours, the first thing the divers needed to do was use the bathroom. For the record there was a pee jar in the sub with us for obvious reasons, but most of us avoided using it at all costs.

While the day’s divers used the restroom, other science team members would quickly carry all samples collected off of the subs and into the laboratory.  In the lab, we would photograph each living and fossil coral sample. Living coral samples would be stored in various tubes and jars with preserving chemicals to maintain the live tissue through the rest of the voyage and post-cruise shipment to the PI’s university for biological analyses. Sample processing was followed by dinner, and after dinner we held science meetings. The entire crew aboard would usually gather in the main conference room on the ship, and the pilots would prepare a slideshow of photos and video footage taken using a GoPro from inside each sub during the dives. The student aboard each dive would then have the opportunity to describe what had been observed during their dive and lively discussion would ensue.


Dive days were long and surprisingly tiring, considering we spent most of the day laying down inside the sub. We wouldn’t get to eat much or walk around most of the day. I completed four dives during the course of my time aboard, and I found that to be plenty. That does not diminish how exhilarating it was to know you were one of a very small group of people that has ever dived that deep and seen the places in the ocean you have seen. If ever given the opportunity in the future, I would dive again, especially with the HURL team.
My advice for any scientists about to embark on their first deep-sea submersible diving endeavor would be to pack lots of warm clothing to wear inside the sub, always use the bathroom on the ship before you depart, and take lots of photos and videos of the whole experience.

I was aboard KOK cruise #1716, the final cruise of a four-year field work endeavor funded by the National Science Foundation.
If you are interested in more information, the initial findings of the first few years of research under this project were published here.

Danielle Schimmenti
Department of Geology and Geophysics, Texas A&M University, USA

If you have questions or comments concerning Danielle's post, please leave a comment below, or send her an email. You can also connect with her on Twitter.


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