Surviving 75 hours alone in the ocean

this sounds dangerous. Just curious, why were you in 60deg water for two hours?

The first time I went for a hike without checking the weather. I had a topo and compass but not a GPS (which I almost never carry anyway) and, as it was a day hike, no stove or any overnight supplies beyond a bottle of water. In the summer that's not really a problem (you can almost always survive overnight in summer without a problem even with no preparation, food or equipment, especially if it's not raining) but stupid and dangerous in the winter at altitude. I was wearing relatively lightweight "travel" gear because I expected to be sweating, not sitting still. In any case it began to snow heavily and I could not see any landmarks, much less my map. I tried dead reckoning to the trailhead but eventually came across my own snowshoe tracks as it began to become dark. Very scary. I was also frightened of stumbling into a lake or off a cliff, both which were relatively nearby. At some point the dog became fed up with my antics and just walked away, which he normally never does. Lacking any better plan I followed him and he walked pretty directly to the trailhead which turned out not to be that far away.

The second was much more serious: again, I got a late start because of work and got into the wilderness around dark, not having checked the weather. I skied a bit but it's dangerous to travel at night, especially in the snow. I do have a special lightweight and compact rig I developed for sleeping below zero, but it requires some time and attention to set up. So I put up a tent (least I had brought one!) for me and the dog because I wanted out of the weather and was too tired to try to make a robust shelter, especially in the dark. Unfortunately the spot I chose was exposed and the winds were quite strong, pulling branches down and threatening to pull the tent (I had only anchored it to the snow). In the dark I had to get up, find a tree well, and dig a hole. I put my skis and my pack over the hole, dug a chair, and then spent a sleepless night with my dog. I opened his jacket and my jacket, sat on the dog pad and my sleeping pad, and wrapped my sleeping blanket around us with the dog blanket over the top. I put the dog's jacket under him. He sat up/stood up all night and kept me warm (most of the time I was hugging him). I was afraid to fall asleep and potentially freeze to death because the covering required continuous adjustment. When we dug out in the morning up my tent was gone (I eventually found it) and there were branches that had fallen where it had been, though who knows if they really would have been dangerous? At least it hadn't snowed much, though it was pretty cold.

(One of my students managed to dig a shelter using only his skis when he was caught downhill after skiing out of bounds, but he did the digging before the sun went down, and was rescued in the morning. His ski gear was adequate for overnight in those conditions).

The common thread here is that I was dumb, dumb, dumb and deserved to suffer. I prepare better when writing code than I did on these two trips: I was overconfident that my skills and experience would get me through.

BTW my dog weighed almost 150 lbs (not much less than I do) with legs as long as mine. He had (he's since passed away) well over a thousand trail miles and was trained to stick with me regardless of distractions, which is why it was so shocking when he walked away. He only did that one other time, when a group of us were cutting a trail -- I assume he was bored and went back to camp in the hope of finding forgotten food. Oh yeah, he would also do it sometimes in the office if he thought someone might be eating a sandwich :-).

-Spent over 120 days in the open ocean aboard a 25ft boat.

I have. I find it distinctively easier than pools, lakes and rivers. The commenter is right, it doesn’t take much energy, comparatively speaking.

- Just a guy who has floated on water.

My theory is that I keep less air in my lungs on a normal out breath than others.

When I started training in freediving (apnea), I learned how to take much fuller breaths. I can almost guarantee that if you haven't done that kind of training, strengthened your diaphragm and learned 3-zone breathing, you aren't taking in nearly as much air as you could.

Our bodies are mostly water and the amount of mass that we have that's denser than water isn't that much denser. But water is a lot denser than air and the more you can add air volume, the more buoyant you become. Learning to float is a matter of learning to maximize your volume. Some density numbers from the internet...

Salt water: 1.03g/ml Fresh water: 1g/ml Muscle: 1.06g/ml Bone: 1.1g/ml (approximate...couldn't find a good source for this) Fat: 0.9g/ml Air: 0.0023g/ml

The numbers seem to back up your instructors. As you can see, all these values are fairly close except for air, so adding more air to your volume can dramatically change your buoyancy. Wikipedia lists the average adult male lung capacity at 6L, so a 5L breath should be achievable for most. In salt water, that 5L breath will add more than 5kg of buoyancy, which is enough to float around 400 lbs of muscle or 176 lbs of bone. In fresh water, that same 5L breath will add a bit less, enough to cancel out 193 lbs of muscle or 121 lbs of bone. There's no way that I can know your body composition, but those numbers are very substantial. The more likely is that you're just not getting anywhere near 5L of air in your lungs.

If you're ever into you're trying it again, look up some stretches to open up the lungs. Then practice breathing shallowly with nearly-full lungs. If you're able to do that, you'll probably be able to float laying on your back, where your head is mostly submerged...remember, every part of your body above the surface counts against your buoyancy, for the same reason that air in the lungs matters so much.

Article about it in New Scientist: https://books.google.com/books?id=rYIJJP7audkC&lpg=PA26&dq=g...

Here's the study "Exceptional case of survival in cold water": http://www.bmj.com/content/bmj/292/6514/171.2.full.pdf

They immersed him in 5.3C water for 83 minutes, and only stopped the experiment because of discomfort in his feet. His temperature only dropped by about 1C.

Prolonged soaking in seawater, along with the friction from his wetsuit and fins, damaged Hewitt’s skin pretty badly.

As others have pointed out, beware planning for one environment, and finding yourself in an very different but adjacent one. Warm air, cold water, no pants.