JFC In Yoko -- A Study In Black And Brown

USS Jefferson City (SSN 759) arrived in Yokosuka today for a port call; here's a picture, with USS Kitty Hawk (CV 63) in the background:

It seems like this is a fairly standard picture that Fleet Support in Yokosuka sends out for every submarine that arrives; check out the similarity to this picture of USS Chicago (SSN 721) pulling in there back in June.

There's one difference between the two pictures, though -- check out the vent line by the aft cleat in both places. The hull by the runoff from Chicago's topside vent line is clean; here's a blowup of the same area on the JFC:

So what did JFC put into their seawater systems to make that mess? Was it something that attracted some really, really big birds and gave them diarrhea? Did they cross-connect their sanitary system in some horrible way? Was it a prank? Some disgusting whale mating mistake?Have I just completely forgotten what that connection is supposed to be used for, and it's actually just a horribly mispaced san overboard fitting? You decide... and let us know in the comments. Whoever comes up with the best and/or funniest explanation gets the admiration of their peers.