Electromagnetic waves do not travel through water; sound waves, however, do, through pressure changes. Electromagnetic waves travel at the speed of light, 300,000 km/second; sound waves, at 1,500 km/second, and, being mechanical, their speed varies depending on the conditions of the medium through which they propagate, the water temperature, etc. Sound waves exhibit the effects of reflection and refraction, meaning they do not travel in a straight line, unlike electromagnetic waves in air or a vacuum.