The speed of light in water is approximately 75% of the speed of light in a vacuum. This means that the speed of light in water is approximately 299,792,458 meters per second x 0.75 = 224,848,343.5 meters per second, or roughly 224,848,343.5 x 0.000621371 = 139,741,965.8 miles per second.
It’s worth noting that this value is not constant and can vary depending on factors such as temperature, salinity, and the presence of other dissolved substances. The speed of light in water is also dependent on the wavelength of light, some wavelengths travel slower than others in the water.