I've read where it's best to have a change of clothes in the truck in the event you do turtle/fall in, etc., during the winter time or cold water temps to prevent hypothermia. I've gotten wet from my knees down before in 45* water, and changed clothes quickly in the parking lot. Did not care that the lot was full of people, I got those wet clothes off in a %^&$%$ hurry. LOL.
I found some polar tech wader pants at Dicks's for ~$30, similar to the sleep pants available but heavier material that I wear under my waders, the pants have straps at the cuffs to prevent them from riding up when pulling on the waders, are comfy and warm. I drive to the lake and home in them, and have worn them under my rain suit pants before and work good.