River Luna

A major river that runs from Lake Zarovich (North of the Town of Vallaki) to the south, through the Bogs of Berez and then out west past the border of the mists.
  Many [Barovian]s know it is unwise to travel down the river via boat. It's rapids can suddenly speed up or slow down and many have become trapped in the strange mists that seem to roll through the area. Many strange creatures appear all along the river. Some claim to have seen spirits of people they once knew, now trapped by the mists.