One of the lost thrills of seagoing science were the Swim Calls. After having just completed a hydrographic station or recovering the Pegasus instrument we might – if the seas were calm and with the master’s permission – take a moment to relax with a brief jump into the ocean. What a thrill that was. Imagine swimming in the Gulf Stream with the bottom some 3000 m down. Dive down around the hull of the boat which in the clear blue waters looks like a gondola floating by overhead.
I got a taste for swim calls pretty early in my career. One of my mentors, Prof. Martin Mork, and I were talking about building an instrument to explore the small-scale the small-scale velocity field that must be associated with the fine structure we were seeing in the salinity and temperature versus depth profiles. Martin suggested that if I were to build such an instrument he would invite me to try it out in the Mediterranean later that summer. That was an offer I couldn’t refuse and quickly whipped together a free-falling instrument with a hot-film anemometer to do just that. He had arranged for an 8-day cruise on their research vessel Helland-Hansen out of Malaga, Spain. We tried the instrument and it seemed to work but we had no clue what it was telling us. What I remember best of the cruise were the swim calls we had every day, sometimes in the morning and every day in the afternoon. Tired of always working in Nordic waters, the University of Bergen oceanographers had decided to spend a summer doing research in the warm Mediterranean. The Norwegians took these swim calls seriously. We were 16 men onboard, 8 crew and 8 scientists. On at least one occasion everyone – I mean everyone - dropped what they were wearing and jumped overboard. The ship was abandoned!
On another cruise off Kenya in the Indian Ocean on the NOAA research vessel Researcher we had one (and only one) swim call. This was a serious affair. A crane lowered a small platform to float alongside the ship which we would reach via a rope ladder hanging over the side. The platform was a safety measure since it would enable a quick out of the water if needs be. Officers on the bridge would keep a lookout for sharks, and one of them was armed with a rifle. Again, what a thrill it was to view the ship from below in the crystal-clear waters of the Somali Current.
I suppose it was inevitable that with increasing concerns about safety swim calls would become a thing of the past. My last swim call was on our research vessel the Endeavor. And this only because the relief captain on this cruise took a more nuanced view of the situatioon; a lovely day, a good gang, and a pestering chief scientist. This was second of two month-long cruises to study what we called the Anatomy of Gulf Stream meanders. It was a glassy calm Sunday in April in the middle of the Gulf Stream. Some of us climbed down the rope ladder while others just plain jumped in. Two of the students, Jules and Kathy, were true nayads fearlessly jumping from the bridge deck. Somewhere on my laptop I think I have a video of them splashing about. Those were the days.
Let me end with a little story from my mother’s husband Al Woodcock. He was in charge of many of the hydrographic cruises on WHOI’s research vessel Atlantis throughout the 1930s including numerous sections across the Gulf Stream. A section means stopping every 30 nautical miles or so to take a hydrographic station. Each station required two, maybe three casts lowering a set of Nansen bottles and reversing thermometers to increasing depths. He told me that the first thing he might do when he got up was to take a dip if they were on station. No problem at all if you are in the Sargasso Sea or warm Gulf Stream. So, coming up on deck one morning he jumped in as he was wont to do. He was in for a shock; he didn’t know that they had crossed the stream and were in cold water from the Labrador Sea!