plecos fine, the skimmer is beside the pond in a 4'x3'x2' deep hole that has a liner inlet into it. the pleco pulled the liner out of the inlet to the skimmer which started water draining into the rest of the hole, he then worked his way down into the mud and was digging beneath the skimmer and pushing it up. once it got too high and the pump started to make more noise from sucking in air, he simply swam back into the primary pond. I checked him he doesn't have any scars.
so now as hindsight shows, the whole skimmer area will be lined and some buildup will be placed to prevent him from getting into it.