If I could start over, I would do 70 degree once, 60 degree once, then 50 degrees about 5 times. After that, I would fill a tub--or cooler--with icecubes and water and stand or sit in it for just a few minutes.
After experiencing 32 degree water, you will never have to experience anything colder than that (unless you deep sea dive in the antarctic). Now that you know what 32 degree water feels like, you can judge your progress as to when you are brave enough to take a 32 degree soak.
The first time I did it, I filled the tub with cold water and ice until it was about 35 degrees, I sat as submerged as I could in it for about 10-15 minutes, then pulled the plug and turned on full hot until it got up to 50 degrees, then soaked there for 30 more minutes.
The next night, I got the water to 32.5 degrees and sat in it for 30 minutes. The 3rd night I did 45 minutes. Since then, I have done 33-35 degrees 7 or 8 times, like every couple weeks just to keep it fresh in my mind.
What I found in 33 degree water: You don't shiver at all until 20-30 minutes after you are out and dry off. This is because your body shuts off all peripheral blood flow to protect the core organs from hypothermia. When you get out and warm up, the cold blood from your limbs and skin get into your core and induce a shivering response. With 70 degree water, you don't experience vaso-constriction and the cooled blood flows freely to your core causing instant shivering.
Also, 33 degree water tightens all exposed skin in a way that will blow your mind. Look at your kneecaps when you are in there, they are like leather pads with strange divots and dimples that I still can't quite figure out. Your skin will turn a cheery pink. Fat cells exposed to this temp for very long will literally kill themselves as the fat congeals and destroys itself--this is called apoptosis and occurs at a temperature just above freezing. Temps at freezing or below will kill skin and tissue (frostbite), but temps just above freezing will kill subcutaneous fat. This is how Zetiq works.
Sorry for the novel...