In regards to cold water...
I've fished in creeks wearing stocking foot hippers when the water temp was in the high 30's or 40’s and I wasn't moving a whole lot so when I did move, I could barely walk my feet were so numb. In those situations a boot foot wader or hipper is the only way to go.
I've also wet waded the Codorus in early spring when guys in waders stared at me in disbelief because THEY were cold so my point is it's all relative to your comfort level. Even on those days on the Codorus after the initial shock and numbness, I was fine.
Another advantage to wet wading is it gives me a great feeling for the water temps on a trout stream during warmer months BEFORE I double check with my thermometer.
I still remember one day sharing my beer stash with a landowner sitting on his porch before heading into the woods to fish a Schuylkill Country Class A. Class A or not, as soon as I stepped into the stream I knew it was warm. My thermometer confirmed my suspicions so I walked right out to the surprise of the guy on his porch.
I know I would have taken that water temp at some point during the day but if I was wearing waders or hippers and didn’t instantly know it was warm, I doubt it would have been the first thing I did after getting in the water...
Regarding things people fear like ticks or infections...
Can't ticks get on the parts of your body above the water line and what if you have an open cut and you waders leak?
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