Boats are used to transport resources across water.
‣ - a small wooden boat that can carry a few resources.
‣ - a larger boat that can carry more resources but can only dock at the ‣
Boats are built at the ‣, which must be placed on the shoreline so the constructed boats can be launched into the water. Once a boat is ready to sail you need to select it and assign it either to an Expeditions to create a new harbour on unclaimed land or set up a transport route between existing harbours.
You can assign a boat to stop at harbours (‣/‣). Once a route is confirmed the boat will automatically travel between your harbours and resources will automatically be able to find their way through the routes you set.
By default, at every boat stop, the harbour stackbots will load all types of resources onto the boat. You can change this by adding rules to a boat stop. You can also set import and export rules for a whole harbour. For full details check out the Transport Rules section.