AFTER LANDING AT SAN JUAN, THE ACFT WAS PARKED AT THE CUSTOMS AREA, THEN WAS TOWED TO GATE 15 & LOADED FOR THE NEXT FLT.THE PUSH-BACK WAS SUCH THAT THE CREW HAD TO TAXI TO THE GEN AVN PARKING AREA & TURN AROUND BFR PROCEEDING TO RWY 8 FOR DEPARTURE. WHEN CLEARED FOR TAKEOFF, THE WND WAS FROM 160 DEG AT 11 GUSTING 22 KTS. AT APRX 120 KTS ON THE TAKEOFF ROLL,A LOUD RUMBLING SOUND OCCURRED WHICH INCREASED RAPIDLY, THEN THE ACFT BEGAN TO VIBRATE. AT APRX THE V1 SPD OF 141 KTS, THE CAPT REJECTED THE TAKEOFF USING MAX BRAKING. UNABLE TO STOP ON THE REMAINING RWY, HE ANGLED THE ACFT TO THE SAFEST AREA. THE FLT ENGR'S BACK WAS INJURED AS THE ACFT HIT THE REIL SYS. THE ACFT STOPPED WITH ITS NOSE IN A LAGOON. DUE TO TREES, WTR, ACFT ATTITUDE & ONE ACCIDENTAL DISARMING, ONLY 4 OF 8 EMERG SLIDES WERE USED. A LAB ANALYSIS INDICATED THAT THE #7 TIRE HAD FAILED DUE TO LOW INFLATION, MOST LIKELY FROM FOD. DURING THE ABORT, ITS COMPANION TIRE FAILED FROMOVERLOAD. BLACK MARKS ON THE TAXIWAY REVEALED THE #7 TIRE STARTED LOSING PRESSURE WHILE THE ACFT WAS TAXIING.