A DSNDING B737-300 FLC EXPERIENCES A POTENTIAL CONFLICT WITH A CLBING DH6. THE DH6 WAS ON A VISUAL SEPARATION CLB FROM THE B737 BUT; ACCORDING TO THE PIC OF THE B737; HE GOT TOO CLOSE FOR COMFORT.

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ON DSCNT FROM FL190 TO CLRED ALT OF 13000 FT MSL; WHILE ON 118 DEG HDG (VECTOR) TO DEN. PASSING 17000 FT ATC CHANGED ALT CLRNC TO 16500 FT FOR TFC. SIMULTANEOUSLY OUR TCASII ADVISED US OF TFC AT 15600 FT CLBING. THERE WAS A BROKEN CLOUD LAYER AHEAD BTWN 15000 FT AND 17000 FT. OUR DSCNT RATE WAS NEAR 2000 FPM. BY THE TIME WE ARRESTED THE DSCNT; WE BOTTOMED OUT AT 16300 FT AND IMMEDIATELY CLBED TO 16500 FT. DURING THE DSCNT; THE TCASII GAVE US A 'REDUCE DSCNT' FOLLOWED BY A 'CLB' ABOUT THE TIME WE WERE BOTTOMING OUT AT 16300 FT. THE OTHER ACFT WAS FIRST SEEN AT OUR 12:30 O'CLOCK POS; AT APPROX 1 NM HEADING APPROX 330 DEG HDG. WHILE GOING TO OUR 9 O'CLOCK POS; THE ACFT CONTINUED TO CLB AND TURNED TO A 290 DEG HDG. AT OUR 9 O'CLOCK POS THE ACFT WAS LESS THAN 500 FT VERT AND BTWN 1000 FT AND 1500 FT HORIZ STILL CLBING. WE MAINTAINED LEVEL AT 16500 FT AND TCASII CONTINUED ADVISORIES. BTWN OUR 7 O'CLOCK POS AND 5 O'CLOCK POS TCASII SHOWED THE OTHER ACFT AT 16400 FT AND AN INDISTINGUISHABLE DISTANCE. WE ADVISED DENVER APCH OF OUR INTENT TO FILE AN NMAC RPT. ONCE ON THE GND AT DENVER INTL I CALLED OUR COMPANY AND THEN DENVER TRACON. THE SHIFT SUPVR AT TRACON TOOK MY VERBAL NMAC RPT. SHE IDENTED THE OTHER ACFT AS A DASH 6 THAT WAS OPERATING WITH VISUAL CONTACT TO US. IT WAS AN ACFT INVOLVED WITH SKYDIVING. THAT HE WAS OPERATING WITH VISUAL CONTACT WAS NOT TOLD TO US AT THE TIME OF THE NMAC.