Answer: light slows down when it moves from air into water.
Step-by-step explanation:
1) As correctly stated by Cleo, the light changes direction when it moves from air to water. That is what is called refraction.
2) Refraction is defined as the bending of the light ray due to the change of medium.
3) Refraction happens as much as the light goes from air to water and as water goes from water to air.
4) Since the water is an optically denser medium than air, the light ray will slow down when the ray pass from air to water, and will speed up when the light ray goes from air to water.
5) When the light passes from the the optically less dense medium (air) to the denser one (water) the light ray bends toward the normal (which Cleo described correctly). When the light ray passes from the denser medium (water) to the less dense medium (air) it will bend away from the normal.