Sea turtles can hold their breath for up to seven hours underwater, depending on circumstances. A sea turtle's level of activity while underwater determines the length of time he can hold his breath.
Sea turtles are reptiles that require oxygen to breathe. A sea turtle engaging in low levels of activity, such as during periods of sleeping or resting, can hold his breath four to seven hours underwater. A sea turtle engaged in vigorous activity uses oxygen more quickly and must return to the surface for oxygen more frequently. Turtles caught in nets or other stressful situations may use up their oxygen quickly and drown in a matter of minutes.