There is no available conclusive evidence as to which side of the island the main channel flowed, and it may have changed over time given shifting silt of the Sundarbans delta. India claimed that a 1981 detailed survey of water depths showed the main and much deeper channel and main flow on the east side of the island, which favored India. Similar survey data was printed on a 1990 British Admiralty chart and reprinted on the 1991 US National Geospatial-Intelligence Agency (NGA) chart number 63330 Edition 9 at 1:300,000 scale.