Superhydrophobic leaves retain a thin gas film on the leaf surface when submerged in water. The gas films facilitate gas exchange with the floodwater thereby partly overcoming the 10,000-fold slower diffusion of gasses in water compared to in air. In light, the enhanced gas exchange increases the flux of CO2 into submerged leaves so that underwater net photosynthesis is greatly enhanced in leaves with gas films compared to leaves without. In darkness, the leaf gas films facilitate the diffusive flux of O2 into the leaves from the surrounding floodwater so that dark respiration is sustained. In this chapter, we discuss the effects of leaf gas films during submergence with focus on rice as well as on wild wetland plants possessing superhydrophobic leaves.