Dickens notes that the Thames Police force district extends
   from Battersea to Barking Creek. It is composed of 98 men, 
   eight duty boats and two supervision boats. The police wait 
   silently in dark places. One of the Thames Policemen, whom 
   Dickens called "Pea", tells Dickens that the reason for 
   lurking quietly in the dark is that "River thieves can 
   always get rid of stolen properly in a moment, by dropping 
   it overboard. We want to take them 
with the property, 
   so we lurk about and come out upon 'em sharp. If they see us 
   or hear us, over it goes." Theft is aided by the ability of 
   the Thames river thieves to meld into the 
   
tiers of boats in the pool at night.