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Lake Simcoe Temperatures January 4, 2018

Posted by Chris Sullivan in CCR.
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As is it the closest body of water to my house I dive in Lake Simcoe relatively often. The drive takes about an hour, compared to 3 to 4 hours to the admittedly much more interesting diving in places like Brockville and Tobermory. While I’ve managed to do both of the latter sites as day trips, it is an arduous proposition compared to going somewhere from which I can get home by lunch time.

Simcoe is relatively shallow, with a maximum depth of about 42 metres and an average depth of 15m over its 725 square kilometre surface area. The deepest spot is the middle of Kempenfelt Bay, quite close to the hamlet of Shanty Bay where we shore dive, so we can get some depth there if we’re prepared for the cold water. As there are few fish, no wrecks, no reefs and nothing much but weeds and silty bottom, aside from looking at what was put there intentionally, garbage thrown overboard by passing boats, flotsam like deck chairs blown in from shore and the occasional golf ball, one can pass the time by doing drills and studying the marine environment.

This latter pastime caused me to stumble of the World Lake Database. The Lake Simcoe information dates from the mid 1980’s, and contains the following table of temperatures by month.

Station K45, 1984 
Depth May Jun Jul Aug Sep Oct
0 4.8 14.8 17.2 22.2 13.7 12.0
5 4.8 14.5 17.3 22.2 14.5 12.0
10 4.8 12.1 15.6 22.2 15.1 12.0
15 4.8 9.3 13.9 15.1 15.2 12.0
20 4.8 7.7 8.5 9.9 10.4 12.0
30 4.7 7.6 8.0 8.1 6.7 12.0

Depth is in metres, temperature in degrees Celsius. Station K45 is in the open water of Lake Simcoe, not in Kempenfelt Bay. There is a station in Kempenfelt – K42 – but so far I’ve not found any similar data from it. The October data looks suspicious with completely uniform temperature down to 30 metres, but I noticed from my own experience that the temperature becomes more uniform in the late summer so perhaps it is the case. 12C is quite a reasonable temperature so there is no reason to hang up the fins just because summer is over.

The chart below summarizes the water temperatures during my dives this year. In July my dry suit failed on a dive in Tobermory, Ontario and so everything after that is in a relatively thin wet suit, with nothing deeper than 20 metres or colder than 12 Celsius (and not for very long at that temperature I can assure you). Even the dry suit dives were curtailed somewhat because my hands were too cold.

You have to look at the chart’s legend to figure out when the dives took place. The ones that start above 20C are in July and August, the and the ones below 15C are from May and June. By the 12th of September, there was little difference in temperature between the surface and 15 metres.

The data were collected on my AP Inspiration EVP rebreather, which records depth, temperature and many other data points every 10 seconds to a precision, although not necessarily an accuracy, of 10 centimetres and 1/10th of a degree Celsius. For each day’s diving all of the data were summarized to the nearest metre by averaging the temperature readings. The result is not a dive profile, but a thermal profile by depth.

Simcoe Dives 2017

So the temperature difference by depth is greatest in the mid-summer months. By September, the temperature at depth is higher than in mid-summer. It is considerably warmer than the September average in 1984, but the dive was only 1 day in September and in a different part of the lake, so it would be hard to draw a conclusion from that difference, although the City of Barrie has published a Climate Change Strategy which indicates that there is warming trend in Kempenfelt Bay based on K42 data.

I’m looking forward to gathering a lot more data in 2018 after the ice melts. The broken dry suit has been replaced with a better one, including a thicker hood and for the first time ever, dry gloves! So next time there should be a lot more data from the depths.


Climbing Back Up the Hill November 11, 2016

Posted by Chris Sullivan in CCR, Emergencies, Fitness and Nutrition.
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Until recently I did not dive enough. I started to forget how much I enjoyed it. In 2015 I only dived a couple of times, and I started to wonder whether I was going to give it up altogether. I also let my weight creep up to almost 190 pounds, putting me just in the “Overweight” category of the Body Mass Index (BMI). I wasn’t exercising. My clothes were too tight.

Fortunately I signed up for a Florida Keys wreck diving trip last April and had a great time. The experience renewed my resolve to get in shape and I then and there decided to bring my weight down below 180. I didn’t have to do a whole lot to make that happen. My diet rules were pretty simple.

  • Avoid bread – not completely but most of the time. I love bread, but now it is more of a treat than a compulsion.
  • Lunches were mostly vegetable smoothies or soup (without bread!). Later, I found a bean salad recipe that I really like, and if I’m at work and haven’t brought anything in I’ll get some take out Sushi or Sashimi.
  • Avoid overeating at any single meal. I can easily wolf down large quantities of pizza. Now I limit to 2 slices.
  • Avoid free food. In our society there are countless opportunities to consume excess calories, like someone bring doughnuts into the office or all-you-can-eat buffets. No longer.

These simple rules worked so well that my weight just kept dropping. By July I was in the mid 170’s, and I was slightly affronted when I attended my physical and my doctor said that my BMI was a bit on the high side at just under 24. Then came the opportunity to conduct a Wreck Diving course in August. That went quite well but I thought I was working too hard even though I’d been getting in better shape working in the garden all Summer. I had to do more exercise.

Meanwhile the weight kept going down. After a long weekend of diving doubles I decided I was going get a CCR (closed circuit rebreather) and felt that there would be a benefit in getting into better shape so I started a simple exercise program. It consists of walking an incline on a treadmill for 30 minutes or so every day, 20 minutes of stretching, and doing some crunches and push-ups every other day. I  walk outside instead of using transit or driving when there’s time. To increase cardiopulmonary capacity the incline will go up by 1% (about 1/2 a MET) each month, so by midsummer 2017 it will be at the treadmill’s maximum. I’m also managing my diet by consuming more protein through food or the addition of protein powder to make up the calories burned by the exercise.

Now I’m down to 160 pounds – way less than I’d planned. BMI is 22, close to the middle of the normal range. There’s still some fat around the midriff but further weight loss is not in the plans. For the next phase I’m going to stay at 160 and try to change body composition with exercise. Despite a normal BMI people call me thin. Is that because we’re used to seeing more overweight people these days, including me 6 months ago?

By staying on the diet the current weight is easy to maintain. If below 160, I add a glass of orange juice to breakfast. That’s worked so far but more might be needed. I’m not stressed about it and avoid fanaticism, but embrace discipline.

Like quitting smoking, the hardest part is deciding. Deciding is not the same as wishing or wanting. The rewards are many, with the greatest being the capacity to keep diving for years to come, greater overall health and better fitting clothes. The flip side is that diving provides much of the motivation to keep exercising – a virtuous circle about which I remind my wife often.

Lastly, I’d like to address a common comment that divers often get from their non-diving friends. It goes something along the lines of why would you do something that can kill you? Often we respond with something like “you can die just crossing the street, if we all thought like that we’d never leave our homes”. While I agree, there’s a more fortuitous response, which is more like “By diving, training to dive and staying in shape to dive, I’m actually increasing my chances for survival. I also hang out with people who are trained in lifesaving and like myself can maintain self-control in emergency situations.”

CCR, O2 Consumption & Exercise October 31, 2016

Posted by Chris Sullivan in CCR, Fitness and Nutrition, Technical Diving.
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With a little less than 12 hours diving a CCR, I’m now venturing to comment on a technical aspect of the experience which dawned on me recently. Surely I’m not the first to think about a CCR in this way, but I’ve not come across this analysis previously and wanted to record my thoughts about it here.

The more I dive the more I concern myself with staying fit, as I’m not getting any younger, and that gets me thinking about both capacity to expend energy and calorie consumption. Rebreather training tells me that when things are going right, bubbles are only released upon ascent, which is just the excess volume from the loop as the gas expands with the decreased ambient pressure. Other than this, all the Oxygen consumed during the dive is metabolized by the diver.

Fitness evaluations are frequently done by measuring inspired Oxygen, and except for what is released on ascent the CCR will measure that based the change in O2 tank pressure. I found this article that directly relates calories burned to O2 consumption and also relates O2 consumption to METS (metabolic units, a measurement of energy used in exercise) and body weight.

I’ll give an example, which for simplicity I’ll use metric units. My CCR has a 2 litre tank, which can be filled to 230 bar. So its capacity is 460 litres. Say I do a 60 minute dive and the pressure in the tank goes from 230 bar to 180 bar, a consumption of 100 litres of Oxygen. Ignoring the bubbles on ascent, I’ve burned 500 calories (100 litres at 5 calories/litre).

I weigh 72.3 Kg right now. 1 MET energy output uses 3.5 ml of O2 per kg of body weight per minute of activity, so if we know our O2 consumption in litres the average number of METs used in the dive will be (litres x 1000) / (body weight x minutes x 3.5). So if it were me doing this dive my average energy expended would have been about 6.6 METs, which is a little less than this source gives for slow cross-country skiing.

Coincidentally, according to the calculator on this site, my current treadmill regime of 3.5 MPH at 6% slope also requires 6.6 METs (BTW tomorrow I increase to 7% slope or 7.1 METs).


So I’m inspired (pardon the pun) to think that this yet another great feature CCR diving. I can now, with reasonable accuracy, determine the calorie expenditure on a dive, and replenish accordingly. I also know how hard I’ve been working on the dive and train to that level.

Regarding the bubbles on ascent, there’s probably reasonable way to estimate how much O2 is going overboard. Fodder for a future post, no doubt.