There are no bridges or causeways connecting Seabird Key to the mainland. Guests can only access Seabird Key by boat. Upon your arrival to Seabird's mainland launch site in Marathon, Florida, guests are greeted by our manager. He will assist in loading the luggage onto the 19 Boston Whaler. From the moment you cruise down the canal, only 5 minutes by boat, your private island adventure begins in the Gulf of Mexico.