Water Infrastructure Now Public-Private Partnership Act or the WIN P3 Act - Directs the Chief of Engineers to establish a pilot program to evaluate the cost-effectiveness and project delivery efficiency of allowing non-federal interests to carry out authorized flood damage reduction, hurricane and storm damage reduction, and navigation projects. Requires the Chief: (1) to identify not more than 15 projects authorized for construction; (2) to develop a detailed project management plan for each identified project that outlines the scope, budget, design, and construction resource requirements necessary for the non-federal interest to execute the project or an element of the project; (3) to enter into a project partnership agreement with the non-federal interest at such interest's request to provide full project management control for construction of the project or element in accordance with plans approved by the Chief; (4) following execution of such agreement, to transfer specified amounts to the non-federal interest to carry out project construction; and (5) to regularly monitor and audit each such project being constructed by a non-federal interest.

Sets forth restrictions on projects selected. Authorizes the Chief to: (1) provide technical assistance to the non-federal interests for compensation, and (2) waive or modify applicable federal regulations if doing so would provide public and financial benefits.

Directs the Chief, before entering into a project partnership agreement, to enter into an arrangement with an independent third party to conduct an assessment and provide justification that the proposed agreement would represent a better public and financial benefit than a similar transaction using public funding.

Terminates authority to commence a project under this Act five years after its enactment.