What is the speed of light underwater?

The speed of light underwater is approximately 225,000,000 meters per second, which is about 75% of its speed in a vacuum. When light travels from air to water, it undergoes a change in speed due to a change in the medium's refractive index. The refractive index of water is higher than that of air, causing the light to slow down. The exact value of the speed of light underwater can vary slightly depending on the specific properties of the water, such as its temperature and salinity.