Special Effects Challenges

[Cindy C.]

We've talked a bit about how the PS/SS special effects were done, and 
what worked and what didn't.  That made me wonder how easy or 
difficult the special effects will be in the next three films.  In 
other words, which scenes in upcoming films might pose the most 
difficult special effects issues?

The scene that sounds like a special effects and logistical nightmare 
to me is the Second Task in GoF.  Harry has to sprout gills and 
flippers, swim, fight grindylows, talk underwater, and save some 
students.  Fluer and Cedric need bubbleheads, Krum has to be a shark-
man, and all of it has to be underwater.  I don't even know whether 
it is legal or advisable to have child actors actually do any 
underwater work, so they might need to use stunt doubles or some 
effect to simulate being underwater.

Are these issues insurmountable, and has anything like it even been 
done before?  Are there other scenes in CoS, PoA or GoF that present 
similar special effects or logistical problems?

Cindy