LB
https://en.wikipedia.org/wiki/Whirlpool
A whirlpool is a body of rotating water produced by opposing currents or a current running into an obstacle.[1][clarification needed] Small whirlpools form when a bath or a sink is draining. More powerful ones in seas or oceans may be termed maelstroms. Vortex is the proper term for a whirlpool that has a downdraft.
Sounds like a metaphor for draining a swamp..