Jason is swimming in his backyard pool and notices that sounds underwater are different than sounds above water. What best explains the difference in sounds?

The different speed of the sound waves in water and in air.

Explanation:

Sound waves are defined as the mechanical waves that are resulted from the vibrations back and forth of the particles of the medium through which the sound is moving.

The speed of the sound is faster in water than in air. Sound travels much faster in water than in air. In air the speed of the sound waves is 343 meter per second while the speed of the sound waves in water is 1480 meters per second.

In the context, Jason who is swimming in his pool hears sound differently underwater and above the water because of the difference in the speed of the sound waves above the water and in water.