The only real sounds transmitted in the water are those that come from
the animals that live there.
You're right, the above statement's not true. There's a lot of other underwater noise besides that which
comes from animals. Some of it originates at the boundary where the Earth's
tectonic plates collide. Boat and ship propellers or breaking waves at the
surface make noise, and so do fishermen who sometimes use dynamite to stun
fish, which are then easily collected.