My interpretation

Actually, I like your interpretation. He seemed to sink too deep into the ocean to be rescued, then he saw a white light, he went to the light and a hand reached out for him.... it's all evocative of death and heavenly salvation. That interpretation didn't occur to me simply because I don't think about god(s) much. But I wouldn't be surprised if the filmmaker purposely filmed the ending that way to spark discussions like the one you and I are having.

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great answer... 100%

He is reading out the message that he put in that glass jar and dropped overboard from the raft.

I also thought he was rescued. The reason I think this is that I thought we were inside of his head, and seeing his perspective, which was influenced by his state of mind.

So, even though we (the audience) saw a visual depiction of him sinking fast in the end (much faster than I would expect), I think he was just telling himself he was rapidly sinking with the raft on fire 25-50 feet above him. He had given up, having lost everything, and probably thought the boat in the distance didn't see him, just like he had been passed up before, by passing ships. Instead of that fast sinking, he was probably just below the surface and the search light from the small boat easily found him, he could see it, and someone reached down to him.

As a point of comparison in another part of the film, he caught a fish but a shark snagged the fish he caught before he could bring it on board. This startled him and he began staring into the water -- and he literally saw just one shark swim by. But the camera angle suddenly shifts and we are deep in the ocean looking up at the raft and we see dozens of sharks swimming around his raft. I think this is his mind imagining and exaggerating this threat of one shark. There may have been more than one, but I don't think all those sharks were reality. Just as the depth of his sinking was not reality.

At least that's how I interpreted those scenes.

Yes, that's what we saw, but the way it was edited (fading to white) made me think it was actually him crossing to the other side, and the rescue part was after his death. How would the rescuer know exactly where he was? as the hand was already there, reaching down as he came to the surface, but it was night time, you wouldn't see someone under the water, the light from the fire would make it even harder to see under water. Seemed a little to perfect if you know what I mean. I think the director said it was left up to interpretation, hate it when they do that, I much prefer a definitive ending.

if there is an elephant in the room, I like to charge for rides

HE WAS JUST HALLUCINATING BEING RESCUED. I THINK THAT WAS PRETTY OBVIOUS. OR THERE WAS ACTUALLY A BOAT. HAND OF GOD? SURE, IF YOU'D LIKE.

IF YOU THINK ABOUT IT FOR A MOMENT, THERE COULD BE NO SMALL BOAT, BECAUSE WHERE DID IT SUDDENLY COME FROM? ALL THERE WAS AS FAR AS THE EYE COULD SEE WAS A SHIP AND THAT WAS MILES AWAY, SO WHERE DID A SMALL RESCUE BOAT APPEAR FROM?

HE HALLUCINATED THIS BECAUSE BASICALLY THE WHOLE SECOND HALF OF THE MOVIE HE IS THINKING ABOUT BEING RESCUED, OR HOPING FOR IT, SO IT WAS HIS LAST MIND FLASH BEFORE HE DIED.

AND ANOTHER THING, IF IT WAS GOD REACHING OUT TO HIM, WHY DOES GOD NEED A FLASHLIGHT? HAHA JUST KIDDING, BUT SERIOUSLY, WHY IS THIS A BIG DISCUSSION?