I'm looking for a film that has a princess in it, trolls (who I think take over the castle) and at some piont near the end there is a flood?

The Princess and the Goblin (http://www.toonhound.com/goblin.htm) (93)

Young princess Irene and a humble miner's son join forces
To protect the kingdom from a goblin invasion. Princess Irene
Discovers a hidden room and finds her magical grandmother who
Offers Irene some guidance and a magic thread that will lead her
Home if she gets lost

view scene 0:40/6:19 (http://www.youtube.com/watch?v=Rc8U2YcPvig&feature=related)