In The Witcher 3: Wild Hunt, Geralt can now sail boats. To use a boat, he must first board the vessel, then take the helm using the .
Running into obstacles will damage his vessel which is divided into six compartments. Once all six are damaged, the boat sinks.
You can Fast Travel while on a boat, but only to destinations accessible via a water route. To Fast Travel by boat, open the World Map panel while at the helm of a ship. You can travel to any point marked anchor symbol ().