Red-eared sliders cannot breathe underwater. They breathe air and must come to the surface periodically to take in oxygen. The frequency at which a turtle needs to breathe depends on how active it is.
During the day, when temperatures are warm and the red-eared slider is active, the turtle may come to the surface every few minutes to breathe. However, at night, the red-eared slider’s activity slows with the cooler temperatures, and it can stay underwater for several hours at a time while sleeping. Red-eared sliders brumate during the winter. They bury themselves in mud underwater and remain nearly motionless for months at a time. During brumation, they absorb oxygen from the water through their cloacal cavities.