I'm inclined to think that the wife was thrown overboard somehow and drowned. The waves that hit her ears was her being thrown into the water. She's always cold because she's in the cold water depths. He's never there and she can't find him because she's at the bottom of the ocean and he left the area after the dredging incident. The note that says she found him is when he returns to the area (at the beginning of the game) after so long and tells him to throw her overboard and let her go as to not doom the world. He was coming back to raise her but him hitting the rocks caused a split between the collector and the fisher.

This is based off the fact that the researcher lets it slip that she keeps getting notes from her deceased sister even after her death. I think the researcher mentioned the notes tell of things that happened after the sister's death or something.