If so, it would have still been there when the tank stopped feeding and subsequently have been pumped into the wings.
No suggestions, just facts on how the fuel system works....
Woodpecker... there are "facts".. and then there are "insufficient facts".
On the 777, there are jet pumps for scavenging fuel and there are jet pumps for scavenging water.
The pickup points for the jet pumps for water are at the very lowest point in the tanks and pick up small quantities of water throughout the flight and mix this with fuel to be burnt in the engines. In these small quantities, they present no problem to the engine (who knows.. it may even improve the performance of the engine???).
The jet pumps for fuel are in the centre tank and help get rid of the 900kgs in the Centre Tank. These do not begin operating until the fuel in the wing tanks goes below a certain level (c/o a system of valves and floats).
This type of system has been operating very well on all Boeing aircraft for, literally, many decades.
The ultrasonic water detectors fitted to the 777 have trigger points of 31.8 and 627 litres per wing/centre tank respectively. Clearly, there would have to be an enormous amount of water to even be of concern to the 777.
Note: this data is from the Boeing Maintenance Manual which may differ from the pilot's manuals from time to time.