Long Island Sound Restoration and Stewardship Act This bill reauthorizes the Management Conference of the Long Island Sound Study, the Long Island Sound Stewardship Act of 2006, the Long Island Sound Grants, and Long Island Sound Stewardship Grants through FY2023. The bill amends the Federal Water Pollution Control Act (commonly known as the Clean Water Act) to direct the Environmental Protection Agency's (EPA) Office of the Management Conference of the Long Island Sound Study to include in studies on strengthening the implementation of the Comprehensive Conservation and Management Plan for Long Island Sound: (1) environmental impacts on the sound watershed; and (2) planning initiatives that identify areas most suitable for various activities in order to reduce conflicts among uses, reduce adverse environmental impacts, facilitate compatible uses, or preserve critical ecosystem services. The office must: (1) develop and implement strategies to increase education and awareness about the ecological health and water quality of the sound; and (2) monitor progress toward meeting the goals, actions, and schedules of the plan. The limit on the federal share for certain grants for projects and studies to help implement the plan is revised by increasing the limit for grants other than citizen involvement and education grants. A federal agency that owns or occupies real property, or carries out activities, within the sound watershed must: (1) participate in regional and subwatershed planning, protection, and restoration activities; and (2) ensure that the property and activities are consistent with the plan to the maximum extent practicable.