Bats are able to fly safely in complete darkness, whereas humans cannot rely on sound in the same way.
(i) Explain the mechanism by which bats avoid obstacles at night.
(ii) State two reasons why this mechanism does not help humans to navigate in the dark.
(iii) Would a bat be able to use the same mechanism effectively when it is completely submerged in water? Give a reason based on the properties of sound in different media.