Some people make a big fuss of a cold mikva - there is something to it, but Rabbainu didn't leave us any specific directives about doing so, and it more of a general "seegoof" (self affliction) than a tikun (rectification) of the mikva.
Rabbainu gave two amazing directives about going to the mikva.
1. Stay under until you need to come up for air (you can speed up the process by exhaling all the air in your lungs rapidly). Although he didn't elaborate, one can easily understand the amazing strategy behind this, because coming out of the mikva is like being born new, so by getting rid of all the old breath (neshama/soul), one can rise and receive new breath (neshama)!
2. Dip 310 times - some people claim that each dip must be a full dip with head and maybe even shoulders out of the water and back in - personally I can't see any reason in the world why that would be so, even by removing a tiny tip of your finger would terminate that dip, and by reinserting it, another dip would have been achieved. Thus with two fingers, one can alternately remove one and insert the other at an extremely fast rate, and probably in one minute can do 310, if you want to play it safe, use one finger (so there's no overlay...), and you can still do all 310 in probably two minutes.
The main mikva is G-d as it says, mikva Yisroel Hashem... and from Him comes the effervescent gushing wellspring, the river which purifies all defects: Na Nach Nachma Nachman MeUman!
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