[He keeps rowing, his expression an impassible mask. It's not the frown he usually wears, it's literally nothing. As if his own face was unable to pull out an emotion according to it.]

I couldn't safe you. The only way I knew to try to safe you failed, so I made the choice I've always done in those circumstances. Rather than let someone else have your body and use it to do things you didn't want to do, I killed you with my own hands and killed myself in the process.

[He doesn't really expect her to understand. He doesn't think anyone could.]

I thought that since the witch was Davy Jones' enemy he wouldn't bring you back, neither could she. So you would be able to rest in peace until everything was over, or until I gathered that stupid jewel and wished for you to be returned to live and sent home where you would be safe. Maybe strike a deal with Davy Jones, I'm not sure, but I would have found a way.

[Even if it meant being stuck in that world, or not seeing her ever again.]