Yes, that would be my guess. When I had a similar issue, I alternated, pushing backwards from the pump, pushing forwards from the skimmer, back and forth. I eventually just lined up my closest skimmer, turned the pump on, shoved ahose in the bottom of the skemmer and pudhed with the hose/pulled with the pump until it cleared. If you have access to a boroscope, you could try to scope backwards down one of the pipes. Based on the fact you said it was swamp, I'm betting something got sucked into your suction line and it is blocking it. How long did you run the hose for? and how well were you able to seal behind it? I would think the 20-50 psi most municipal water systems run at should have been enough pressure to push anything backwards.