There are two types of Water Terrain: shallow water and deep water.
By default, water tiles have a Quality with a base value of 10.
Lake shown on the map
Shallow Water[]
This is the area near deep water, it is usually found around rivers and lakes, indicated by a light blue coloration.
Shallow water can be used to Dig for Clay or filling a Bucket with Water. River Pearl Mussel can also be found in shallow waters.
Deep Water[]
Deep water, which has a darker blue color, can only be traversed by riding on a Boat or Swimming (swimming is highly dangerous!)