Wis. Stat. § 30.15: Penalty for unlawful obstruction of navigable waters.

(1) Obstructions penalized. Any person who does any of the following shall forfeit not less than $10 nor more than $500 for each offense:

(a) Unlawfully obstructs any navigable waters and thereby impairs the free navigation thereof.

(b) Unlawfully places in navigable waters or in any tributary thereof any substance that may float into and obstruct any such waters or impede their free navigation.

(c) Constructs or maintains in navigable waters, or aids in the construction or maintenance therein, of any boom not authorized by law.

(d) Constructs or places any structure or deposits any material in navigable waters in violation of s. 30.12 or 30.13.

(3) Each day a separate violation. Each day during which an obstruction, deposit or structure exists in violation of sub. (1) is a separate offense.