Does Wielder of Waters get +2 might from a hidden spell or hidden unit (like Teemo) attached to a battlefield control?

Ruling: Wielder of Waters gets +2 might from hidden spells, but not from hidden units. The effect is "while" so it updates in real-time.

Sequence:

• While a unit is hidden, it does not count toward Wielder of Waters' bonus
• When the hidden unit is revealed/flipped out, Wielder of Waters loses the +2 might
• Hidden spells continue to provide the +2 might bonus

Nuances:

• The "while" wording means the effect continuously checks and updates based on current game state