I saw a snapping turtle yesterday getting a breath of fresh air along the narrow strip of open water along the bank of my pond, the pond is still 95% iced over. It slowly slide back under the ice as I got closer. The link belows explains how they manage to survive with an ice cap on the water and no gills.

https://www.pbs.org/newshour/science/the-secret-to-turtle-hibernation-butt-breathing