Question

Does light travel slowest in air or water? How can you tell?

Answer 1

Light illuminates deliberately through the waves of H2O due to the immense amount of pressure and loss of O2 that prevents the microorganisms from reaching the end.

(Ps. This is not plagiarized; I spent a lot of time figuring out the answer. :)

Answer 2

Light travels slower in water because it has a thicker wall between the surface.