If the light is traveling straight up, then it hits the interface (surface
or boundary) between water and air perpendicularly (90° to the surface).
This direction is the direction of the 'normal' to the surface. So the
angle of incidence is zero, and that means the angle of refraction is
also zero. The light just keeps going in the same direction when it
emerges into the air, and is not bent.
However, its speed increases in air, and that means its wavelength
also becomes longer than it was in the water.
