How to use a high-level spell.

What does Water Magic have to do with it? It's clearly referring to the Dimension Door spell.

Or Fly, or Town Portal, or Walk on Water. They are also high-level spells. But Water Magic really has nothing to do with it.
Either the author is looking at the wrong part of the book, or they don't have enough Wisdom. Although, considering the phrase

how to use high-level spells that are not used in battle.

A logical question arises: can Katjushka use, say, See Air or Invisibility?