"What these two countries could not achieve from years of talking, has been resolved by global warming," said Professor Sugata Hazra of the School of Oceanographic Studies at Jadavpur University in Calcutta.
Anyone wishing to visit now, he observed, would have to think of travelling by submarine.
The island never rose more than about six feet above sea level. Professor Hazra predicts more islands in the Indian Ocean will vanish as sea levels rise. Link -via J-Walk Blog
As Joanie pointed out early on, this was a mud/sand bar. And yes, India and Pakistan dispute - because their boundary was stupidly based on the river channel, which has (as they do) shifted.
Want a description of the phenomenpn? Perhaps Mark Twain's LIfe on the Mississipee would do. When he worked as a riverboat pilot "islands" changed daily, and a pilot had to be careful even some were fairly predictable.
http://news.bbc.co.uk/2/hi/south_asia/8584665.stm