Bicycle theft is one of the easiest crimes to discourage: Simply lock your bicycle when it is not in use.Thieves are looking for an innocuous crime with a quick getaway, and a bicycle locked to a fixture like a bike rack or pipe presents neither. In the event your bicycle is stolen, a registration can provide a quick method for locating you should your bicycle be recovered - most stolen bicycles on Tybee are used for a short period and then abandoned. The police will typically impound the bicycle and wait for someone to report the theft.
Although the TIPD no longer has a bicycle registration program, you can try to register with two different national registries. You should probably try both, as we don't know enough to be able to recommend one over the other. If you find a bike, you could check these registries, and if you've lost your back after registration, be sure to report it stolen or missing to improve your chance of recovery!
One claims nearly 6000 stolen bicycles returned, while the other doesn't say. The other has an app for iPhone and Android, while the first one does not. Neither seems to charge a fee. Check them out: https://bikeindex.org/ and/or https://project529.com/garage/.