There is no airport on Harbour island, visitors will need to fly to North Eleuthera ( the airport code for North Eleuthera Is ELH). It is the closest airport to Harbour island.
After passing bahamian customs and immigration, you will exit the tiny airport and will find plenty of taxis for you. Taxis are honest and very kind , rates are predetermined 5$ per person to get to the dock where boat taxis will take you to Harbour Island. The trip duration will take a whole 5 minutes. When getting out of the taxi some locals will offer their help to carry your luggages to the taxi boats located 30 feet or so from the curb. Tipping them will be a good custom if you need their help.
Usually taxi boats are waiting, they will wait to be full in order to leave. It usually takes just a few moments. The cost per person to travel the short distance to Harbour Island is 5$ to the main dock, if you prefer to be dropped off at one of the other marinas close to your hotel or vacation rentals the cost will be elevated to $ 6 per person. The boat trip will take from 5 to 10 minutes depending on the number of stops.
From there you will either be picked up by the hotel or luxury vacation rental operator or will need to hire a taxi or to rent a golf cart in the vicinity of the dock.