Wis. Stat. § 30.71: Disposal of waste from boats equipped with toilets.

(1) In this section, “outlying waters” has the meaning given in s. 29.001 (63).

(2) No person may, while maintaining or operating any boat equipped with toilets on the waters of this state, dispose of any toilet wastes in any manner into the water.

(3) No person may operate for compensation or reward an establishment that has the capacity of providing berths or moorings to 5 or more boats that are equipped with toilets and that is located on an outlying water of this state unless the establishment provides adequate fixed onshore disposal facilities for disposal of toilet wastes from the boats for which the establishment provides berths or moorings. If the establishment is unable to provide fixed onshore disposal facilities due to problems of accessibility to the boats, the establishment shall provide adequate portable disposal facilities for these toilet wastes.

(4) Any rules necessary to carry out the purposes of this section shall be promulgated jointly by the department of safety and professional services and the department of natural resources.