Port and Waterways Maintenance, Development, and Improvement Act of 1981

Port and Waterways Maintenance, Development, and Improvement Act of 1981 - Title I: Findings, Declaration of Purposes, and Definitions - Declares that Congress finds it in the national interest to maintain and develop a viable marine transportation system within the United States, including a network of commercial deep-draft seaports, inland shallow-draft ports, and a multipurpose domestic waterway system to accommodate the needs of the foreign and domestic commerce, promote economic stability, and provide for national security.

Title II: Cost Recovery - Imposes specified tonnage charges on all international commerce commodities at the time of entry into or exit from the United States in order to recover 50 percent of all costs associated with operation and maintenance expenditures of the Army Corps of Engineers directly allocated and attributable to commercial navigation.

Directs the Secretary of the Treasury to promulgate a rate system sufficient to cover such costs. Requires that such charges shall be deposited in the Inland Waterways Trust Fund (hereafter known as the Ports and Waterways Trust Fund).

Authorizes the Secretary of the Army, acting through the Chief of Engineers, to utilize such funds for the Federal share of operation, maintenance, and construction of deep-draft (including the Saint Lawrence Seaway) and inland shallow-draft waterways.

Directs the Secretary to recommend biennially to Congress that specified new construction projects be authorized. Authorizes certain projects only after agreement that a non-Federal public body will reimburse the Federal Government for 50 percent of such projects' costs.

Requires completion of such reimbursements within the life of the project concerned but in no event more than 50 years after the date the project is available for use.

Prohibits the Federal Government from collecting fees for improvements to the navigable waters of the Great Lakes or the Saint Lawrence Seaway constructed before the enactment of this Act. Terminates existing authorizations providing for recovery of any costs for such improvements.

Authorizes such non-Federal public bodies to recover all or a portion of their shares of the project costs through: (1) existing funding sources; and (2) user fees.

Grants the consent of Congress to any port authority to collect, in the form of a duty of tonnage or ad valorem duty, a nondiscriminatory seaport user fee from vessels or cargo engaged in foreign trade.

Authorizes the Secretary of the Army, in consultation with the Secretaries of State, Commerce, Transportation, Treasury, Energy, and Agriculture, the Attorney General, and the Director of the Office of Management and Budget, and with the approval of Congress, to promulgate regulations and guidelines concerning such fee collections.

Title III: Project Authorizations - Authorizes non-Federal public bodies to develop new navigation construction projects without congressional authorization if they agree to pay 100 percent of the costs of such projects.

Title IV: Reports to Congress - Directs the Secretary of the Army to prepare specified reports for submission to Congress.