SHIVER Pirates
This unit of canal patrol SHIVERs have stopped simply supplementing their wages with bribes and protection money and moved to outright armed robbery and kidnappings for ransom when nobody else but them and their victims are looking. It is only a matter of time until murder comes into the mix, probably as a measure to remove witnesses at first.
Notes:
Yes. Basically it comes down to the SHIVER-River rhyme and not much else. Just added the barest amount of colour to that.