Getting unnecessarily wet
From BearWiki
Claim: Getting wet when it's not absolutely necessary in a region where it can get cool is a bad idea.
Since going down a river is photogenic, Bear often spends a great amount of time in the water. Whenever he encounters a body of water, it seems he must somehow get wet from it. In regions with hot nights or when one's clothes will be well dry before night, there is nothing wrong with cooling down in water. However, hypotherma is a very common condition in survival situations, and getting wet is an excellent way to bring it about. Hypothermia does not require freezing temperatures. Stage 3 (acute, life-threatening) hypothermia occurs when body temperatures drop below 90F/32C, and death usually occurs around 86F/30C.[1]. Any outside temperature lower than 86F/30C has the potential bring you to this point if heat is drawn away faster than it is replaced, and water is very effective at drawing away heat. Evaporation can cause materials to become even cooler than ambient temperatures.
As always, taking unnecessary risks when your life isn't in immediate danger is bad advice. Survival alone in the wilderness is dangerous enough on its own. Compounding it with needless risks to save a few hours is a bad choice.
[edit] Analysis
Support: Most mountain rivers are extremely cold, primarily because they are created by melted snow that hasn't had much time to absorb solar heat. After recently being in a river over 75 miles from the sierra crest (in 90+ degree weather) the water was already numbing by 3 minutes. Major hypothermia probably wouldn't have set in until an hour, but common sense immediately made it clear that floating down a cold river @ 4mph was a worse idea than hiking @2-3mph (not to mention the rocks banging your ass in mild whitewater, ouch...feet fwd only does so much).
Support: All Bear would have to have done was watch Deadliest Catch during his nights in the hotel rooms to figure out what a bad idea getting wet in cold water in an area where hypothermia is a common risk is. Around 80% of all the deaths in Alaskan crab fishing is from hypothermia, and almost all of those cases are because somebody fell into the Bering Sea without a proper survival suit on. The Bering Sea averages 37 degrees Fahrenheit, well above freezing, but if you fall into it, your body temperature will drop so fast that without proper life-saving clothing to protect you from the cold, you'll be dead in about 10 minutes. Bottom line: Never, ever, jump in a mountain river without cold water survival gear unless you're suicidal.
Support: It should be noted that this was the scene with the infamous "Hidden PFD." Bear did acknowledge in chat (and only after being confronted) that he was wearing a PFD. Although I have no actual evidence, I do wonder if he was also wearing a wet suit underneath his clothes - there was a black collar visible that was never in any of the other scenes from this episode.
Support: Per Ron Hood (the Survival Consultant for the pilot): "He jumps into a 38f river and floats down it like a "Watery Hiway".... that temp will kill you in minutes. (He was wearing a wetsuit and float vest and got out every couple of minutes to warm up)" [2]
