Hindu: The screen came to life with a bearded middle-aged man named Lalmohan Sheikh aboard a boat pointing to the horizon and saying: “There used to a church over there during my childhood but the hungry river gobbled it up.” This was the opening scene of a documentary film produced by a non-governmental organisation that was premiered here in 24 Parganas district recently. Launched in the presence of Governor Gopalkrishna Gandhi, the documentary, “Mean Sea Level”, depicts the threat …