Only a licensed waterman can present a boy for binding -

seven years an apprentice, learning to row, with long paddles, 

the punts that hold fifty tons of cargo, iron hull, timbered deck,
     greasy gun’les, walked with toes turned in.

Seven years to learn
       the moods and feelings of the Thames,

come to terms with the wind,
      names of points, reaches, bridges, wharves and tidal sets,
while blisters grow until they form,

burst and form again.