I would not recommend soaking negatives or prints in water. Negatives are extremely delicate and sometimes, even the softest cloth would scratch them with ease, wich is particularly bad for film scanning. If you have negs or slides with fungus, I would suggest the use of "tri-cloretileno" (I don't know its name in english) wich is, by the way, extremely poisonous. Some kind of 60,s, 70's & 80's colour prints can totally fade when in contact to water.