I doubt anyone would have found her. In fact, they had drifted very far from the original dive site. It would be like looking for a needle in a haystack. And as the above poster noted, she had no idea if anyone was looking for them, or even if there was any chance that she would be found. With the Sharks circling her at the end, it appeared her death was imminant anyway.

It probably could have saved her, but she had no idea it was coming, so she gave up and let herself die.
I don't feel enough for you to cry.
Oh well.

Open sea is a big place and human head a very small object to spot. Add the drifting effects and helicopter would have large area to search, making it a very big effort even if being in time.

It wraps up the unknown true activities, in showing that she gave up and drowned herself. If she had waited, chancing the sharks didn't attack her, she might have been saved.