I booked the tour online with Yamasa and I showed up 45 minutes prior to boarding to pick up my ticket at the Nagasaki Port Terminal Building.
The weather was calm and I was very lucky to be able to land on the island. The path on the island has no elevation or stairs. The English guide did an excellent job and there was ample time to look around and take pictures.
I did not get a chance to hop onto the island because the operator said that the waves were too rough. The tour is in English on Tues, Thursday, Saturday & Mandarin on Mon, Wed, Fri. The ferry took about 40 minutes to reach the island & then circled around to show passengers the different sides of the island and gave some explanation.
The site is off limits on most days ivo weather or other reasons. However, the ferry tour around the island is comfortable with entertaining guides and english options (i could borrow an english informatic guidebook). The island is quite remarkable and really looks like a battleship. The island looks desolate and eerie, but that adds to its unique charm as such structures are rare in todays day and age when old is often quickly replaced with new. Definitely worth an experience when in Nagasaki.
I have been there twice. Not only an incredible place because of its history: a mine island in the middle of the ocean, totally abandoned some years ago; but also, it is an amazing example of how nature recovers its places when the human is not close.
Definitely you have to visit Hashima island.
Hashima Island, also known as Gunkanjima or "The Battleship Island", is an abandoned mining colony, one of the many uninhabited islands of Nagasaki Prefecture.
What started as a seabed coal exploitation in 1887 grew to a fully fledged city, with its own Pachinko (something like a casino) parlour, only to be abandoned in the '70s with the mine depleted.
Appointment as UNESCO World Heritage Site (as part of Japan's Sites of Japan's Meiji Industrial Revolution: Iron and Steel, Shipbuilding and Coal Mining) was surrounded by controversy, as it was a site of force labour prior and during the World War II - many miners were Chinese and Korean.
The island became a tourist attraction only recently, being off limits until the 2000s. Since it's abandonment, the buildings haven't been maintained, being subjected to the harsh elements (e.g. typhoons); therefore, although in original conditions, they have been damaged and are not safe for exploration.
Although ruin enthusiast might go crazy when they hear about the place, be advised that you cannot actually enter the buildings (or, better said, what's left of them), as visitors access is restricted to a concrete consolidated walkway which covers only on a small part of the island.
The island is accessible only as a guided tour through a 45 minutes ferry trip, but be aware that there are only 2 trips scheduled everyday (morning and noon), so be sure you are not late! I think the trip is cancelled if the weather is bad.
I found it one of the best places to visit in Nagasaki, albeit a little expensive (around 5000 Japanese Yen).