Leithriel's Tolkien Homestead

Nienor and Tar-Miriel survived.

The text only states that Nienor jumped into Teiglin, not that it killed her. Likewise, the text only says that Tar-Miriel was swallowed by the waves, not that it killed her. And as we know, Ulmo has a penchant for saving good people when it is in his power to do so. He saved Voronwe from the shipwreck, after all.

And in both of those cases, he had the power to do so. He saved them both, enabling them to start new lives somewhere else.

And since Hurin also jumped into the sea, he was saved too.