Answer:
Let's assume that the light ray is entering the water from above so it isn't also passing through the wall of a container.
As the light ray enters the water it will be refracted toward the vertical. This means that if it is already vertical, it won't be refracted at all. The change in the angle of the light ray as it enters the water is related to the refractive indices of the air and water. Let's call the angle between the light ray and the vertical in air theta1 and the angle between the light ray and the vertical in the water theta2. Then, according to Snell's law:
{sin(theta1)/sin(theta2)}={n2/n1}
where n1 is the refractive index of air, and n2 is the refractive index of water.