THE STUDENT PLT STATED THAT AFTER DINNER, WHICH INCLUDED A SMALL AMOUNT OF WINE, HE WENT TO THE ARPT TO CLEAN HIS ACFT, THEN ELECTED TO GO FOR A SHORT FLT. HE INTENDED TO STAY WITHIN 25 MI OF THE ARPT, BUT FOUND HIMSELF OVER LAKELAND.HE LANDED AT A STRIP TO CALL, BUT THERE WAS NO TELEPHONE, SO HE TOOK OFF AGAIN. WHILE RETURNING, THE PLT DIVERTED TOWARD THE WEST TO AVOID A STORM. SUBSEQUENTLY, DARKNESS OCCURRED & THE STUDENT BECAME LOST & DISORIENTED. HE SAW A HIGHWAY & FLEW ALONG IT WHILE TRYING TO IDENTIFY A FAMILIAR LANDMARK. EVENTUALLY, THE PLT FLEW OUT OVER THE EDGE OF THE GULF OF MEXICO & INADVERTENTLY DESCENDED INTO THE WATER. AFTER COMING TO REST, HE CRAWLED OUT OF THE ACFT & FELL INTO THE WATER, BUT GOT BACK ONTO THE WING OF THE ACFT. HE REPORTED THAT WHILE HE WAS WAITING TO BE RESCUED, HE RINSED SALT WATER & GASOLINE FROM HIS MOUTH & DRANK FROM A BOTTLE OF GINGER ALE. A BOTTLE OF WINE WAS FND IN THE ACFT. A CHECK OF THE PLT'S BLOOD SHOWED AN ALCOHOL LEVEL OF 0.07 GM% (0.07%) & A TRACE OF DIAZEPAM.