Marco looks like a golf island and is not one, at least not in the way a visitor expects. There are two courses on the island itself and you almost certainly cannot play either. Island Country Club, an 18-hole par 72 first laid out in 1966 by Dave Wallace and reworked in 1991, is member-owned and private. Hideaway Beach Club's nine-hole executive course, 1,844 yards to a par of 32, sits inside a gated beachfront community and is open to members and their guests by invitation. No amount of charm at the gate changes either answer.
What visiting golfers actually do is cross the water. Both courses associated with the island's largest resort sit on the mainland in the Marco Shores area off Collier Boulevard, roughly a fifteen-minute drive over the Judge S.S. Jolley Bridge. The Rookery at Marco is the headline, a course laid through shallow wetland and rebuilt in 2014 by Peter Jacobsen and Jim Hardy to around 7,100 yards from the back tees. Hammock Bay is the other, a par 72 running between live oak and water that holds Audubon International's Gold Signature Sanctuary certification, a designation only a small number of communities worldwide carry. The resort runs a complimentary shuttle to both, on the hour from early morning until mid-afternoon, with a reservation required.
Access to those two runs primarily through the resort. If you are staying elsewhere on the island, do not assume a public tee sheet. Call the golf shop, say where you are staying, and ask directly, because the answer changes with season and occupancy and no article can be current on it.
The island's golf history is better than its access. Gene Sarazen, the first player to win all four majors and the man who holed the double eagle at the 1935 Masters, lived on Marco for decades and had a hand in the 1991 rework of Island Country Club. The park at the island's south end carries his name, with two bronze eagles in flight marking the shot. That is a genuine piece of golf history sitting on a public beach access, and it costs nothing to stand in front of.
The wider truth is that this corner of Florida has an enormous amount of golf and almost none of it is on Marco. Drive twenty miles north into Naples and the density of courses is among the highest anywhere in the country, with a spread from resort-private to genuinely public. A Marco-based golf trip is really a Naples-area golf trip with a beach at the end of it, and planning it that way produces a much better week than hunting for a tee time within the city limits.