Rose: All right both of you, answer me this. When I last stood on this beach—on the worst day of my life—what was the last thing you said to me? Go on, say it.
The Doctor: I said "Rose Tyler."
Rose: Yeah, and? How was that sentence gonna end?
The Doctor: Does it need saying?
Rose: And you, Doctor? What was the end of that sentence?
[He leans closer, takes her arm gently and whispers in her ear] I love you.
The following excerpt is borrowed from a fanfiction called "Same As It Ever Was" by onlylyin on LJ. The author captured their relationship beautifully for this moment in time:
She thought of the other Rose who stood just over there, watching her cry. She wished she could tell that other self that the tears were genuine. It almost surprised her, how easily they came. But she cried in the same way that she did during sad old movies, in anticipation of the pain ahead and resignation towards the ending to come. She went through the movements and she knew she was doing the right thing by letting him let her go. She was letting them both choose, in a way.
Donna spoke, and Rose remembered the trick about spoilers - they never revealed all the details of the story. She should have guessed he was human, could have known, but she hadn’t. Not quite. Her fingers slid inside his coat and her eyes met his as she felt his one heart beat under her palm. She not only knew this was right, she began to believe it. This was a man who wouldn't be broken by loving her. This was a man who knew how to swim.
He told her “I love you. Always have, always will.” His lapels were in her hands and she kissed him; she kissed them both. It is her ‘hello’ and ‘goodbye’ and ‘I love you’ and ‘I know’.
She tasted -his- ‘Forgive me’ on the tip of his ‘Forever’.