Fukuoka has some small islands nearby. They are only a short boat ride away from the Fukuoka shore.
One of them is called Nokonoshima Island. It lays off Meinohama in Western district of Fukuoka City. 10 min by boat from Meinohama ferry terminal. it is a perfect day trip destination. Despite the short distance from Meinohama, it has a slow-paced, country side feel to it. It is a pleasant surprise that there is such a big difference between the mainland Fukuoka and Nokonoshima despite the short distance between them.
In the spring time, you can enjoy the rape flowers in Nokonoshima Island Park, which is about 10 min bus ride from the Nokonoshima ferry terminal (where you arrive from Meinohama).
Walking around the island is always relaxing. Walking up the narrow local roads and seeing the traditional houses and local cats. Air is cleaner!
If you are traveling towards Western district of Fukuoka, take a day trip to Nokonoshima. I recommend it.