[00:01.18]Three groups of dolphins live close to Lantau Island.
[00:07.54]As the tide comes in, they move with it to feed on small fish or squid which travel with the currents,
[00:15.64]using echolocation to see their prey through the murky water.
[00:23.41]They also use sound to communicate.
[00:28.06]But they face a deafening problem.