The Boston Marriott Long Wharf hotel presented plans for a 20,000-square-foot expansion that would add retail and restaurant space on its ground floor.

Five additions would be built along four sides of the building, according to a conceptual plan submitted to the Boston Redevelopment Authority. The building’s footprint would increase from 64 percent to 84 percent of the lot. In exchange, the hotel’s owners could be required to expand public access through the lobby that is part of the Boston Harborwalk or add a ticket office and waiting room for harbor ferries, Boston Redevelopment Authority consultants said.

At a meeting of the BRA’s Downtown Waterfront Municipal Harbor Planning Advisory Committee Wednesday, neighborhood residents were skeptical about the hotel plan. Residents of the Harbor Towers condo complex objected to music from existing bars such as Tia’s on the Waterfront and said the new attractions would attract a similar crowd.

Representatives for the hotel owners told the committee there are no plans to convert the hotel to condos or other uses.

The BRA has asked the Marriott and owners of other parcels in the central waterfront area to submit ideas for redeveloping their properties while improving public access to the harbor. The agency is developing a municipal harbor plan that would require developers to add public amenities such as food concessions and art exhibits.

The harbor plan focuses on the area between the Hook lobster site and Christopher Columbus Park. If developers propose projects that exceed state limits for open space and building heights on waterfront properties, the BRA could ask them to increase public access or pay for public amenities in the neighborhood. A wish list drawn up by the advisory committee includes new wharf space and public art exhibits, a small park near the Chart House, heated waiting areas for ferries and new food concessions and attractions on Long Wharf.