What was found
DURING 80 KNOT CROSS CHECK DURING TAKE-OFF ROLL, PM NOTED STANDBY AIRSPEED INDICATOR FLUCTUATE AND DROP TO 0 IAS. PM CALLED ABORTED TAKE-OFF. BRAKE TEMPS REMAINED NORMAL. AIRCRAFT REMOVED FROM SERVICE. C/W INSPECTION OF STANDBY PITOT P3 DRAIN COLLECTOR TUBE IAW AMM 34-11-00. FOUND COLLECTOR TUBE COMPLETELY FULL OF WATER. ALL OTHER COLLECTOR TUBES ARE EMPTY. PERFORMED PURGE OF PITOT LINE P3 IN REF AMM 34-11-00. LEAK CHECK OF P3 AND S3.