FLC OF AN MLG FAILED TO FOLLOW THE PUBLISHED VISUAL APCH AFTER BEING CLRED BY ATC.

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WE WERE ON A RADAR VECTOR WHEN APCH ASKED US IF WE HAD 'THE' BAY IN SIGHT. WE SAID YES AND WERE THEN CLRED FOR THE BAY VISUAL APCH. APPARENTLY WE HAD THE WRONG BAY IN SIGHT. OUR POS BEING ABOUT A MI OFF PROMPTED SEVERAL COMMANDS AND INSTRUCTIONS FROM ATC. THIS CONFUSED US AND CAUSED A SLOPPY APCH WHILE THIS DISTR WAS TAKING PLACE. VISUAL APCHS ARE NON-EVENTS DURING THE DAY IN GOOD WX. HOWEVER AT NIGHT; VISUAL INDICATIONS ARE MUCH MORE DIFFICULT AND NOT SO CONFIRMING. MOST 'BAYS' LOOK SIMILAR; ESPECIALLY WHEN AT LOWER ALTS. THE COASTLINES AND LIGHTS SEEM TO BLEND IN MORE AND TOPOGRAPHIC FEATURES DON'T STAND OUT AT NIGHT. THE FMC AND THE GLASS CAN HELP OUT; BUT STILL ALLOW FOR PROBS BECAUSE WE ARE TRYING TO LOOK OUTSIDE TO VERIFY POSITIONS. MAYBE 'PUBLISHED' VISUAL APCHS ARE NOT WARRANTED AT NIGHT. THE MARGIN OF SAFETY ON THIS APCH WAS OK BUT 'REDUCED' DUE TO THE CONFLICTING 'BAYS' IN SIGHT. INCIDENTALLY; ATC NEVER ASKED US IF WE HAD THE ARPT IN SIGHT. IF THEY ARE USED; THEY SHOULD BE PREDICATED ON A LANDMARK THAT PLTS UNFAMILIAR WITH THE AREA CAN EASILY 'DISTINGUISH' AT NIGHT TRAVELING 4 MI PER MIN ACROSS THE GND.