Let’s say you had the misfortune of falling overboard during a boating outing in the middle of Lake Michigan. Assuming that you were wearing your normal clothing, the following chart gives an approximation of your survival time given various temperature scenarios:
| IF THE WATER TEMPERATURE (F) IS: |
EXHAUSTION OR UNCONSCIOUSNESS |
EXPECTED TIME OF SURVIVAL IS: |
| 32.5 | Under 15 Minutes | Under 15 – 45 Minutes |
| 32.5 – 40.0 | 15 – 30 Minutes | 30 – 90 Minutes |
| 40.0 – 50.0 | 30 – 60 Minutes | 1 – 3 Hours |
| 50.0 – 60.0 | 1 -2 Hours | 1 – 6 Hours |
| 60.0 – 70.0 | 2 – 7 Hours | 2 – 40 Hours |
| 70.0 – 80.0 | 3 – 12 Hours | 3 Hours – Indefinitely |
| OVER 80.0 | Indefinitely | Indefinitely |
There are two things to note with regards to this chart:
1. These scenarios do not factor in swimmers who are wearing cold water gear such as wetsuits or neoprene caps.
2. The type of open water swimming we engage in does not involve sub-50F temperatures.
The natural conclusion is that, while swimming for 20-40 minutes in 50F – 60F water may not always be the most comfortable experience, it isn’t really a dangerous one.
This is the first in a series of posts that will focus on cold water swimming. I will be covering a number of areas specific to this topic including gear recommendations, what to expect in the water, and – yes – even hypothermia. Hopefully, by taking some of the mystery out of cold water swimming, we can learn to enjoy this experience safely and without apprehension.
What about cold water swimming without a wetsuit? Any danger with swimming in water temperatures around 58-64 for say, 30 minutes?
Hi Brian. I’ve done 30+ minute swims in water as low as 55F without a wetsuit, and I have never had any problems. I don’t have a lot of body fat, but I made sure to prep myself with a cold shower about 40 minutes prior to the swim. That made a huge difference.
Hi Dave. Thanks for writing! This chart is more of a “quick and dirty” approximation of survival time for an average non-swimmer who is suddenly and unexpectedly exposed to colder water (i.e. a capsized boat with people in “civilian clothes”). The Channel swimmers are much more acclimated to sub-60F temperatures, plus they’re generating a lot of heat with their exertion. Still, I can’t imagine being in there for that long, either!
Check out my post on cold water gear under the “Equipment & Gear” category. I outline what I wear under various temperature ranges.
What about channel swimmers and such? Don’t they swim for like 15 hours in sub 60 degree water? I assume this chart is for someone who is not accustomed to swimming in cold water, right?
This is an interesting topic. Obviously there is some variation among people. I went swimming in the lake for my first time a week ago and while I was fine in my wetsuit, others really struggled with the cold.
I would be interested in seeing a similar chart on what temps you will swim in and when you need a wetsuit, and when it is too hot for a suit.
Great site btw. I really enjoy it.
EXPECTED
TIME OF SURVIVAL IS:
Thanks for letting us know this – was this supposed to make us feel better lol.
Great blog by the way.
Cheers.