With its emerging system identity, the sanctuary system was giving thought to what other areas of U.S. waters should be considered for addition. In 1983, NOAA decided that the List of Recommended Areas was both unwieldy and unscientific, and completed the Site Evaluation List (or SEL), a scientifically rigorous and publicly reviewed list of sites that included a number of future sanctuaries, including Monterey Bay, Olympic Coast, Hawaiian Islands Humpback Whale, and Thunder Bay. In 1995, NOAA decided to deactivate the SEL so that it could focus on managing several newly designated sanctuaries.

Today, as numerous communities are expressing their interest in having a sanctuary, NOAA is analyzing the possibility of reactivating the SEL. Reactivation is being considered as part of the Strategic Action Plans to implement the National Policy for the Stewardship of the Ocean, Our Coasts, and the Great Lakes. This action would be to "characterize and prioritize marine areas of national significance, including consideration of ecosystem services, by reactivating [the SEL]." A new SEL would be the first step in a renewed scientifically driven, publicly vetted process to expand the protection of the sanctuary system to new areas.