My vague memories of doing the Short Round 5+ years ago a few times was that I never worried about the mud sump and it was usually bone dry, whereas now it seems to always be full even when the Mendips has from what I've heard been really dry and Swildons has had low water levels?
Has something changed that is causing it to fill up? Is there any point trying to bail it? Once it's closed, does it tend to stay closed for the winter these days? Is there kit there for bailing?
Was hoping to do the Short Round at the start of December on a lazy trip and a bit of bailing might be the right sort of silliness, but if (as I've read in other trip reports) two sessions of group bailing failed to open it then this is obviously not going to be an option. I have one of those little pumps that you can hook up to a drill (that I've never used) but I suspect this does not shift that much water (or at that much head) compared to a bunch of people throwing buckets around.