Not all aquatic turtles can breathe underwater, but some have developed methods of getting oxygen while underwater. Some take in water through their noses or mouths and get oxygen through their pharynges, while some others take in water through their anal openings, according to the Oceanic Resource Foundation.
Oxygen can be absorbed through skin at the throat or through specialized sacks in the anal area. There is also at least one species with gill structures in the anal area that help with respiration underwater. Turtles can hold their breath for extended periods of time, up to three hours in some species, and can better handle carbon dioxide, reducing how often they need to breathe.