B737-400 CREW HAD AN NMAC WITH A C208 IN BFI CLASS D AIRSPACE.

Narrative

NEAR MISS. WE WERE CLRED HARBOR VISUAL TO RWY 13R AND ENTERED ELLIOTT BAY BELOW 2000 FT. BOEING TWR RPTED 'TFC AT 11 O'CLOCK POS TO THE PARALLEL RWY; HE HAS YOU IN SIGHT.' WE DID NOT SEE THAT TFC DESPITE 3 SETS OF EYES LOOKING FOR IT AND PROCEEDED ONTO RWY 13R; OFFSETTING SO AS TO STAY CLR. WHILE WE WERE ALIGNING WITH RWY 13R; BUT NOT YET ON STRAIGHT-IN FINAL (W OF TXWY B) WE GOT A TCASII TA FOLLOWED IMMEDIATELY BY AN RA. OUR GEOGRAPHIC LOCATION WAS OVER THE DRY DOCKS/COAST GUARD STATION. WE STILL DID NOT SEE THE TFC SO WE HONORED THE RA. I BANKED THE AIRPLANE L AND SAW THE CARAVAN VERY CLOSE AND SEPARATING FROM UNDERNEATH ME. ESTIMATED MISS DISTANCE WAS 100 FT. WE OBSERVED '-01' ALT DIFFERENCE ON THE TCASII RA. THE CESSNA PULLED AHEAD AND LANDED ON RWY 13L. WE LANDED ON RWY 13R BEHIND AND THEN ABEAM THE CESSNA. WE WERE CLOSER IN THE AIR THAN WE WERE ON THE PARALLEL RWYS. IN OUR OPINION; THE CARAVAN WAS AT BEST LINED UP WITH RWY 13R. DURING THE CONFLICT WE HAD NOT YET LINED UP WITH RWY 13R -- WE WERE STILL W OF CTRLINE. I TALKED WITH THE PLT ON THE TELEPHONE AFTER THE EVENT. THE DISCUSSION WAS UNPRODUCTIVE.