There was a shipwreck, and only Scarlett Johansson and a special FX artist survived on a deserted island.
They didn't know each other before the shipwreck, but he did know who she was.
At the beginning it was hard, but as time passed, this guy learnt how to provide food and shelter, he started taking care of her, and eventually she started caring about him. After all, there wasn't anybody else on the island.
He eventually built a cabin, had a potable water supply, and all sorts of little clever commodities, all done to make her life easier. It was the most effort any man had ever done for her, and all the hard work made him fit.
One night after some wildlife attacked and he had defended her successfully, she threw herself at him and they made love. After that, they were, for all intents and purposes, "romantically dating".
But for some reason he started drifting away. Something was bothering him, and she noticed.
"What's wrong?" Scarlett asked.
"Nothing..." he would always reply.