What was found
AT FL 370 IN IMC WE RECEIVED IAS COMPARE TO CAUTIONS. IT WAS DETERMINED THAT THE FIRST OFFICER`S SIDE WAS GIVING INCORRECT INFO, THEN CAPTAINS & FIRST OFFICER`S AIRSPEED INDICATIONS BECAME ERRATIC & DECREASED RAPIDLY, PLI APPEARED AFTER DESCENDING THROUGH FL240 INDICATIONS SEEMED TO BE NORMAL. FOUND WATER IN SYS, DRAINED WATER, OPERATIONS TEST OF SYS IAW AMM 34-15-00. OPERATIONS CHECKED GOOD & NO DEFECTS NOTED.