By the time official records began noting the place, Fat Tong Chau was already small. A population of 12 was recorded in 1911. Writer Austin Coates, who documented rural Hong Kong life in the mid-twentieth century, noted that the village had been founded around 1885 and held a population of 23 by 1955 — all of the surname Ip. Scholar James Hayes recorded 34 residents in 1957–1958. The villagers cut grass, raised sweet potatoes, kept pigs, ducks, and chickens. Their children attended school at Pan Long Wan on the mainland, where the Ip family had over generations intermarried with members of the Lau clan. To reach the market at Shau Kei Wan — the principal outlet for their agricultural production — they crossed the water by sampan. It was a life of carefully maintained routines, entirely dependent on the water that surrounded them on all sides, connected to the wider world by boats and by the ties of clan.

When archaeologists examined the ruins at Fat Tong Chau in 1962, they found a stone slab broken into four pieces. The inscription, translated, reads: 'By the Grace of the Emperor, tributes are accepted from and customs exchange with Annam, which is far away from China. Renovated by the Manager of the Customs Station.' Annam was a historical Chinese name for the Vietnamese kingdom — encompassing what is now Vietnam. The customs station at Fat Tau Chau had been established in 1868 by order of the Viceroy of Liangguang — one of three such posts, along with stations at Cheung Chau and Kap Shui Mun at Ma Wan — to collect likin, an internal transit tax, on the opium trade. Opium smuggling through Hong Kong's waters was intense in the latter half of the nineteenth century, and these coastal stations were the Qing dynasty's mechanism for extracting revenue from trade it could not otherwise control. The station at Fat Tau Chau operated until 1899, when the New Territories lease to Britain rendered it redundant.

Hong Kong has created hundreds of hectares of new land by reclaiming it from the sea — a process that reshaped not just coastlines but the identity of places. Fat Tong Chau lost its islandhood to this process, absorbed into the landmass of Tseung Kwan O and the Clear Water Bay Peninsula during the development of Junk Bay's new town. Before reclamation, the island had formed the northern boundary of Tathong Channel. Afterward, the channel itself changed shape, and the island became a topographic memory. Today the former island sits inland of the coastline, surrounded not by water but by industrial estate and landfill — the South East New Territories Landfill occupies the area to the south. Three Sites of Archaeological Interest mark what remains: the Fat Tau Chau SAI, the Fat Tau Chau House Ruin, and a Qing dynasty gravestone. Archaeological finds from the site are on display at the Hong Kong Museum of History.

There is something quietly striking about the trajectory of Fat Tong Chau. An island with fewer than forty residents, a subsistence economy, and a customs post for taxing the nineteenth century's most traded narcotic — it seems, on paper, like a footnote. But the customs station inscription speaks to the scale of the world it was embedded in: trade routes reaching from southern China to Vietnam and beyond, imperial bureaucracy trying to tax what it could not stop, smugglers working the same waters that the Ip clan crossed by sampan to reach the market. The ruins of all of that now sit inside a modern industrial zone, where TVB City produces television dramas watched across Asia. The island is gone, but its stone slab survived, and the Hong Kong Museum of History thought it worth keeping.