It is approximately 380 acres (150 hectares) in size and is connected to the north bank of the river by a causeway that is covered at high water.

[2] Before 2004, the island had a small community of tenants such as the painter Luke Elwes, photographer Hélène Binet, and philosopher David Papineau.

It was piloted by John Cyril Porte, the managing director of the company, and took off from the deep water channel to the south of the island.

[5] Augustus Agar was awarded the Victoria Cross while stationed on the island and detailed his experiences in his book Baltic Episode.

Charrington established a retreat for wealthy alcoholics on Osea Island, among whom it is rumoured that Walter Sickert was included.

From 2005 to 2010, it was a rehabilitation centre specialising in the treatment of addiction problems and mental health called the Causeway Retreat, managed by former nurse Brendan Quinn.