Welcome Home to Watermark Seaport! MOVE-IN TODAY! Watermark Seaport is a collection of luxury rental high-rise apartments and modern lofts. Located at the heart of Boston's Seaport Square, Watermark Seaport sits at the nexus of the bustling Financial District, burgeoning Seaport and historic Fort Point. Residences range from studios to three bedrooms and are complemented by an unparalleled amenity package.