Intercoastal Shipping Improvement Act - Directs the Federal Maritime Commission to develop and promulgate criteria, standards, and procedures for determining what constitutes adequate revenue levels for a common carrier by water in intercoastal commerce. Defines "adequate revenue levels" as levels which are likely to be sufficient to cover total operating expenses, including depreciation and obsolescence, plus a fair, reasonable, and economic profit or return on capital employed by a common carrier by water in intercoastal commerce.

Sets forth the following criteria to be considered by the Commission in determining adequate revenue levels: (1) the cost of replacing vessels and related equipment used in such commerce; (2) the degree of risk associated with the investment of capital; (3) the prevailing cost of money in capital markets; and (4) the public-interest need to assure that service continues to be provided on specified unprofitable segments of transportation by water in intercoastal commerce.