They can only bond with the adjacent water molecules. And so if we take a look at this particular water molecule, we only have one, two, three of these hydrogen bonds. Now, whenever our water molecule moves or rotates from the surface, it will lose those hydrogen bonds. But it doesn't want to lose those hydrogen bonds because hydrogen bonds are stabilizing. So because on the surface we have this air phase and because the molecules cannot interact with the air molecules, that means the water molecules on the surface will be constrained to that location. They will not be able to move as freely as the molecules inside our water because by moving or rotating on the surface they lose those precious hydrogen bonds.