Finally a topic I can post something intelligent on.
DI water is water that has no dissolved ions in it. It is the presence of positive and negative ions which allow electrons to flow through a solution. Without the ions, there is no attraction for the electrons from the battery, so in theory, you could run a victor under DI water without the need for any waterproofing. Be careful though, it only takes a very little bit of ions to allow electron flow. A simple grain of salt is enough to provide enough ions to conduct electricity in 200 mL of water.