Well, you might catch Legionnaires disease!
Seriously though, just clean 'em out and put it all back together. The oil (as has been mentioned) is normal on any intercooler. The water is moreso on the pd150 engine due to the fact that it's a much bigger intercooler than on the 130, and it does cool the charge air so much better. Moisture is present in the air, and it collects in the intercooler and pipework at the low points. Bacteria grows in there and you end up with the snot you can see.