I don't mean to dredge this up but when the car was found were the doors closed and windows in tact? As in ejection wouldn't have happened? What did his seat belt look like?
Since he was on the job is there any way to make them help?
Its a rollover, windows aren't going to be intact regardless.
I understand the intent of the questions, but ejected or not, if he wasn't in the car, he wasn't in the car. Seat belt not being found locked by the police is a given here.
He could have survived the initial crash and tried to get out, but I don't know if you can tread or swim in that kind of water. I'd guess being freshly concussed your chances are pretty slim in that kind of growth. It doesn't really matter whether he escaped the vehicle conscious or whether he was ejected. The end result is likely the same. The growth here sounds thick enough to slow him down, maybe even prevent him from reaching the surface-- with fresh injuries from the rollover, he's not going to be found camping out somewhere.
If there is gators in there, they'd move immediately on the blood. In a rollover you are likely bleeding from somewhere even if just the nose, or debris like garage door openers slicing your face. Even without blood, that kind of vibration disturbance is going to get attention fast, even from gators not already in the water. Gators from hundreds of feet out might start mobilizing if the marsh is in their usual territory. A gators whole life is about waiting to feel something happen.
I'd figure he was wrecked from the crash and died peacefully-- and I'd rest on that. He may have already dozed off a little before the crash. So not even an "oh fuck" adrenaline moment of fear and regret. WIthout being belted in, he would get knocked out.
Very unlikely he was in a desperate fight for his life while gators swarmed him.