Marathon's housing stock reflects its island setting and tourism economy. The market includes canal-front and oceanfront single-family homes, elevated Keys-style residences, condominiums, and mobile home communities, along with properties oriented toward boating and waterfront access. Development is constrained by the islands' narrow footprint and environmental regulations. The mix of permanent homes, vacation properties, and rentals serves both residents and the Keys' visitor economy.

Marathon extends across several of the Middle Keys islands, including Vaca Key, Knight's Key, and Boot Key, linked by the Overseas Highway. The city's neighborhoods range from canal-front subdivisions and oceanside communities to the denser commercial corridor along U.S. 1. Boot Key, with its harbor and municipal marina, anchors the boating community, while Sombrero Beach Road leads to the city's best-known shoreline.

Marathon offers a relaxed, water-centered island lifestyle. Boating, fishing, snorkeling, and diving are everyday pursuits, and the community's docks and marinas are central to its identity. Residents and visitors gather at Sombrero Beach, waterfront restaurants, and community events throughout the year. The pace is unhurried, and the ocean is both playground and workplace, giving Marathon the easygoing character associated with the Florida Keys.

Marathon's students attend the Monroe County School District, with campuses including Stanley Switlik Elementary, Marathon Middle School, and Marathon High School serving the Middle Keys. The district is notable for its island geography, with schools spread along the Keys. Florida Keys Community College, with a campus in Key West and facilities across the Keys, provides higher education and workforce programs for local residents.

Marathon is connected to the rest of the Florida Keys by U.S. Highway 1, the Overseas Highway, which runs the length of the city and links it to Key West to the south and Key Largo and the mainland to the north. The Seven Mile Bridge, at the city's western edge, is a defining element of the drive. The Florida Keys Marathon International Airport provides general aviation and regional air service, and travel is otherwise primarily by car and boat.

Recreation in Marathon centers on the water. Sombrero Beach offers swimming and snorkeling, while fishing ranges from shoreline and bridge spots, including the Seven Mile Bridge, to inshore flats and offshore charter trips. Diving and snorkeling explore the reefs of the Middle Keys, and kayaking and paddleboarding are popular in the backcountry. On land, Crane Point Hammock provides nature trails, and The Turtle Hospital and Dolphin Research Center add educational attractions that define the community's conservation-minded character.