A very scientific experiment


The idea for this experiment was born after a few dives Tony did last year, wearing his dodgy old wetsuit, in very cold water. He’d emerge from the water almost paralysed, unable to speak, shivering uncontrollably. His muscles would cramp, and he’d struggle to breathe for a time. It’d take him quite a long while afterwards to regain his comfort level.

We wondered just how much a lengthy submersion in cold water affects one’s body temperature when wearing a wetsuit (two 5 millimetre layers, plus a hoodie and gloves). I’ve been trying to remember to take a thermometer with me to dives for months, and finally – on the day of two planned dives in False Bay in early February – managed to remember to pack it into my bag.

Since Tony is now diving in a drysuit on deeper dives, the person whose temperature was to be measured was yours truly. I don’t get as cold as he does – I have more body fat, for one thing, and for another I learned to dive in the Cape and haven’t dived much anywhere else… So cold water is the norm for me. I’m also a hot sleeper, if that counts for anything – my body is quite good at warming itself!

Anyway, I took my temperature before and after both dives. My thermometer isn’t terribly reliable so I took a couple of readings each time and averaged them. Temperatures are in degrees celcius. It was a beautiful, sunny day with a warm breeze. The air temperature was about 26 degrees. Here are the results:

Time Description Temperature
0630 Leaving home for Miller’s Point 36.5
0800 Just before first launch to the SAS Transvaal 36.6
0937 Five minutes after surfacing, dive time 32 minutes, depth 32.4 metres, water temperature 8 degrees celcius 35.0
1040 Second launch to Partridge Point 36.1
1201 Five minutes after surfacing, dive time 38 minutes, depth 21.9 metres, water temperature 8 degrees celcius 34.8

For those of you (like me) who enjoy graphs, here’s one showing the same data.

Graph of body temperature before and after repeated dives
Graph of body temperature before and after repeated dives

We repeated this experiment on two dives of similar duration and similar temperature in the Atlantic ocean, and the results were also a 1.5 degree drop in body temperature which had almost fully reversed itself by an hour after the dive. We’re also going to repeat this experiment on my husband, in his drysuit, to see whether the temperature changes are as extreme. I know they’re not – this time on the boat ride back to the slipway it was me whose teeth were chattering so much I couldn’t eat my Bar One, while Tony displayed a complete lack of sympathy, all snug in his drysuit pyjamas!

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Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

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