If for some reason, all electrical went out to lunch .. all of the major control surfaces might go to neutral? (remember, the 777 is the first fly-by-wire commercial jet) You'd be flying similar to the Sioux City aircraft without hydraulics? Only the engines to control left/right/up/down with? I think you'd have major problems with the up/down .. it might go into a phugoid oscillatory mode. Very difficult to control .. flying low .. you might get an idea of land/water to see where you were, but, you're cooked. You have to figure a place to land, and it's not going to be pretty. But, I'd think that there would be battery power for the critical items .. flight control computers, comm radios? Unless it was some sort of power surge throughout the system?
A320 was the first fly by wire airliner.
B777-You would still have engine driven and air driven hydraulic pumps running.
B777-Spoilers No.4 & No.11 have backup cable controls. So some roll control still.