#1 is hydration, your body can't regulate without enough water. Most of us run on the edge of dehydration especially in Winter when we mainly drink coffee and energy drinks.
Think of it like your car, we need fluids so the elements don't affect us as much, more water = more clean blood flow to the extremities blood is life and warmth.
My .02

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??? Tennis shoes ??? hopefully NOT when it is raining. They tend to get wet. Better option is GoreTex lined jogging, hiking or hunting boots.
...Phone... most everything in cold related clothing these days has a phone pocket..... put the phone in a zip lock bag and put it in that phone pocket. Preferrably in that pocket on your Guide Wear rain jacket. Easy to get to and you will really have only one shot at using it if you are in the water.
... I know it is a pain the A$$,,, but in rainy weather and cold weather have that throwable tied to a long rope and on the deck. It might save a life. Hard to stay afloat with all those layers of warm clothes getting water soaked. The throwable floatation device will help there and the rope can be used by teammate to pull you to the boat.
... One more thing,,, if by yourself,,, never run the TM with continuous power. Hard to catch that boat if you fall in and you are by yourself, especially if you are an "older" person.

Yes Tennis shoes.. If it starts raining I just my rain gear on top of everything and stay dry
the last sentence in the Flippin-Out post is by far the most important