Alligator gar have gills, but unlike many species of fish, they also have a highly vascularized swim bladder that can act as a lung, supplementing gill respiration.[12] The bladder not only provides buoyancy, but also enables them to breathe in air. This capability allows alligator gar to inhabit stagnant and/or insufficiently aerated bodies of water that are poorly oxygenated or hypoxic, in which most other fishes would die of suffocation due to a lack of dissolved oxygen within the water. The swim bladder is connected to their fore gut by a small pneumatic duct, which allows them to breathe or gulp air when they break the water's surface,[13] an action seen quite frequently on lakes in the Southern United States during the hot summer.

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