Not to be confused with the Malaysian island of Labuan off of the coast of Borneo, Labuan in Banten Province, Indonesia, is a bit of a weekend getaway for Jakartans, with its nice beach.
It's in the general region of Carita Beach in the western side of Java but is easier to get to from the capital and is a lot more laid back. Some of the coastline here is fantastic and calm, allowing for good diving and snorkeling. The beach has millions of shells and is fairly quiet and relaxed during the week.
Labuan is also a good place to visit for jumps across the Gunung Krakatau, the volcanic islands of Krakatau and nearby Anak Krakatau that blew its top in the 1800s. The islands are still uninhabited today but treks can be paid to both peaks.
Labuan is closer and easier to get to from Jakarta than Carita, to the north. Soekarno-Hatta Airport, near Jakarta, is the gateway airport, receiving flights from all over the region. It is 3 hours by road from Labuan.