Elly's story *spoilers*

In the car, Elly just got off of the phone with her mom, saying "if anyone calls for me, don't tell them where I am." She doesn't want her fiance to know she's away on a trip.

Elly is smiling and seems to be getting along with Ahmad during the car ride. He tells her a quote in German from his ex when she receives a phone call. He asks if he should pull over and she says "No, I know who it is, I'll call back later." It must have been her fiance. Then she says "so what does it mean?". He translates the quote "a bitter ending is better than an endless bitterness". She has a sobering look on her face and says "that's true", very shortly after being reminded of her fiance.

That night at dinner she retrieves the salt from the kitchen. She's holding it in her hands, alone in the kitchen, deep in thought with a distraught look on her face. (Keep in mind, salt suppresses bitterness). She is then shown engaged in a game of charades, smiling, having a good time.

The next day Elly wants to leave but Sepideh insists that she stay. This makes Elly visibly upset, as she sits on the steps by the shore. Nazy passes by and comments on Elly's (engagement?) ring, whilst also asking Elly to keep an eye on the children. Elly rubs her ring, seems to think about her fiance and stares off into the distance, towards the girls, away from the direction of the boy in the ocean.

Next we see Elly fully enjoying herself, shouting and laughing aloud, while flying a kite. She still hasn't noticed the boy in the ocean as her attention is on the kite in the air. It seems she experiences a sense of enjoyment and freedom at this time (shortly after being reminded of her fiance). The smiles and laughter come to an end and Elly says to the girl "Come on, take it. I have to go."

Where did Elly have to go??

We then see the kite in the sky, and only hear the ocean roaring. So Elly fled, and the older girl is flying the kite.

She must have left the beach right then, because the youngest girl runs to her dad on the other side of the house, saying Arash is in the sea. Elly should have been the nearest adult.

If Elly went into the water, she would still be visible in the next scene, unless she was a very poor swimmer and drowned immediately, or hit her head on the large rocks and drowned immediately. Is that what we are to suppose?

It seems Elly must have noticed Arash was in danger, and went into the water to help him. Otherwise, the two young girls - preoccupied with flying a kite, so far away from Arash - how would they know that Arash was even in danger in the water?

Elly must have left the beach when she said "I have to go". BUT, I understand that HOW she disappeared is not an important part of the story. It is only important that she DID disappear. After all, the movie isn't about Elly.