Yeah, the only part you can't see is the suction pipe and perhaps the 90 that usually exists where the skimmer body attaches to the suction pipe. Snaking it certainly makes the most sense. If that comes up clean, I think the only other likely culprit is in the impeller area....I'm a little skeptical of that unless you had a lot of mud and grit that could've gotten past the pump basket. Let us know what you find.