I still remember my first pond crossing on 242 OCU. Found the fish ok, got to the first chain change and did so successfully. A couple of minutes later my screen nav returned to the flight deck (I had not noticed his absence and being an independent sort of chap didn't seek permission to fiddle with my Fisher Price Activity Set) and instructed me to change back to the original chain and imediately change back to the new 'follow the fish'.
Also remember crossing the pond Westbound, only to find no Loran going East a few days later. Seems they switched the bloody thing off whilst we were Stateside. As a true professional I finished my chicken wings close to top of climb and 'read' them on the return leg.