I was reminded of this phenomenon as we steamed into the Jellingham Channel, leaving Mud Point on our starboard beam. It was after a capsizing disaster here in 1892 that the international law for the size of ships' portholes was changed, stipulating that they must be large enough to allow the escape of a fully grown man. The 2,120-ton British steamer Anglia ran aground at Mud Point and capsized. Five of the crew were trapped below decks in the fo'c'sle, but managed to climb up to the topside port-holes. They were able to stick their heads out to shout for help, but were unable to get their bodies through to escape. A team of rescuers which boarded the overturned ship strained and smashed with crowbars and chisels in a frenzied attempt to widen the portholes before the tide rose. They failed, and when the water closed over the Anglia's hull they were forced to retreat to their boats, where they watched helplessly as the shrieking men were engulfed.
We crossed the Balari Bar with only 16in to spare. Our Pilot slowed the ship to half-speed, to avoid ‘squatting’ - lowering our draught by the greater displacement of water at high speed - and there was a distinct feeling of tension on the bridge. The Captain, who earlier that night had told me this was his first voyage up the Hooghly and he was not looking forward to it, paced back and forth between the radar scanner and the bridge wing. The first mate stood almost to attention beside the wheel, transmitting the pilot's helm orders to the secunny. On the starboard bulkhead the echo sounder was flickering red repeating the same message over and over again - zero, zero. zero. The Pilot sat in the high wooden chair on the left of the secunny, his eyes rarely leaving the river ahead as he read the messages the lights were giving him.
I walked over to him after making another ostentatious scrutiny of the echo sounder, which was still telling us that we ought to be hard aground. With some diffidence I asked him by how much we were clearing the bar. "Sixteen inches," came the unhesitating reply. Could he explain how this calculation was made? He led me by the arm to the front of the bridge and pointed north-west. "You see that single green light on the shore over there? That is the Balari tidal semaphore station, and its light is telling me that the tide on the bar has risen 4 metres above the chart datum depth of 2.4 metres. This ship has a draught of 5.9 metres. I deduct the draught of the ship from the total amount of water on the bar and that tells me that I have enough to get across."
An hour later we dropped anchor in Kalpi Roads, the pilot ordered an anchor watch of one officer and two seamen in case the ship dragged in the five-knot current, and we all went below to our bunks.
Next morning there was a light mist across the broad expanse of the roadstead, draping the fleets of fishing boats in ghostly wreaths that were soon shrivelled away by the ascending sun. It was time to go. Ringing down to the engine room for dead slow ahead to take the tension off the chain. The Pilot ordered the anchor to be weighed and swung our ship into the flooding tide.
We were now heading for the most dangerous stretch of the Hooghly, the Eastern Gut Bar at Hooghly Point, sometimes called the James and Mary Shoal, after the first ship to be wrecked there in 1694. Here the Hooghly takes a sharp bend to the right, just where the Rupnarain, a non-tidal river, flows into it with all the power that you would expect from a daughter of the mighty Ganges. The pilot must make his approach on the flood tide, but as he goes into the turn, his port bow enters the current from the Rupnarain. His starboard quarter is being pushed up-river by the Hooghly flood, while his port bow is being pushed down by the Rupnarain. An insensitive or mistimed helm order at this critical moment can send a vessel spinning out of control on to the James and Mary Shoal, a quicksand that can literally swallow a ship whole.