Merren was rowing and Io was singing to Ehxeyr when the fog came on. Suddenly, and thickly (and with a strange tint, maybe, not that she's an expert on fog.)
The lake has no current and they weren't near shore but she still didn't like the idea of hitting some snag or rock she can’t see. But it's only a few minutes later that the fog disperses.
Their surroundings are not what they used to be.