The air sacs serve to keep the pelican remarkably buoyant in the water .
The air sacs may also cushion the impact of the pelican 's body on the water surface when they dive from flight into water to catch fish .
The air sacs serve to keep the pelican remarkably buoyant in the water and may also cushion the impact of the pelican 's body on the water surface when they dive from flight into water to catch fish .