Cold currents are sweeping along
the coast of Florida.
And with them come grey mullet,
on their migration to their spawning grounds in the south.
Millions of them,
and packed so tightly,
they stay in the water
like an oil slick.
Few people on the beach
are even aware of them.
The mullet keep as close
to the shore as possible.
For in deeper water,
there are predators.
Close to the beach,
they have to keep clear
of human swimmers.
But now, hunters from the open ocean
have detected them.
Tarpon, over two metres long
and weighing over 100kg.
To get close to the mullet in the shallows,
the tarpon turn on their sides.
Now the mullet can't see
their shining, silver flanks
until it's too late.
And feasting begins.
Blacktip shark arrive.
Pelicans join in.
But these attacks have little effect
on the immense shoals.
The mullet outnumber their enemies
by 10,000 to one.
So the great procession travels on
into the northern Atlantic Ocean,
where, at last, they will be able
to spawn in safety.