You are in a metal sphere that is not much wider than your outstretched arms. It is uncomfortable, cramped and cold and there are no facilities. You can't hear any noise from the ocean, but you do hear the noise of the sub. The fan of the air scrubber drones as it takes carbon dioxide out of the air and as oxygen is released from cylinders so we can breathe. You hear the hissing noise of the ballasting which brings water into tanks to sink the sub so we can descend, or expels water to make it lighter to ascend. Propellers churn to move the sub forward and lift props mid-ship adjust the altitude.
That's deep sea scientist Peter Rona describing what it's like to dive in a submersible to the bottom of the sea.
Rona died last week. In exploring hydrothermal vents and ocean ridges, he made more than 100 trips to the depths in submersibles like the American Alvin, Russian Mirs, and Japanese Shinkais. He was the subject of an early 2000s IMAX film, Volcanoes of the Deep Sea.
Rona continues his description:
Descending into the ocean is sheer excitement. There are three tiny windows. One up front is for the pilot and two to either side are for observation. We bring down sandwiches as we can be in the subs for up to 20 hours. Soda is prohibited because it releases carbon dioxide that would throw the meters off scale. If you need to go to the bathroom there are containers for urination. So if you want to be comfortable, don't eat or drink before a dive.
As the dive progresses, it becomes colder because the temperature of the deep ocean outside is close to freezing and penetrates the metal hull, so you bundle up. If the sea is rough on top it takes a while to be recovered and at worst it can feel like you are in a washing machine. But I have never been frightened.
Filming the IMAX film was a challenge. The camera was so large that only the pilot and a camera operator could go down. The camera took the front window and making the pilot drive the sub using a video monitor. The windows are plastic. So if the sub gets too close to the hot vents the windows would soften from the heat of the smokers and implode almost instantaneously. But the pilots are very skillful and this never happened. I have been certified as co-pilot of the sub by the Navy.
The National Oceanic and Atmospheric Administration, where Rona worked for 25 years, continues exploring the deep ocean with submersibles and remote-operated vehicles. For a fascinating fictional exploration of these issues, check out J.M. Ledgard's Submergence.