THE PLT RPRTD THAT DRG TAKEOFF FROM A LAKE, THE ACFT FLEW APRX 200 FT, THEN SETTLED IN A SWAMP. IN A STATEMENT AFTER THE ACDNT, HE NOTED HE HAD 'EXCESSIVE BACK PRESSURE' ON THE CONTROL STICK & STATED THAT MORE SPEED AT LIFT-OFF WOULD HAVE BEEN HELPFUL. ALSO, HE RPRTD THERE WERE CALM WIND CONDITIONS & RAIN SHOWERS IN THE AREA. THERE WAS ANOTHER PART ON THE LAKE THAT WOULD HAVE PROVIDED A LONGER TAKEOFF AREA.