an equator line
It can mean anything but normally it means a river.
A blue line on a map is a lake ,river , or body of water
a blue line on a map means that it is water weather it is a stream river or lake
A blue line represents a river on a map so you know it is a river,a lake, or the sea
I am guessing that's a river.
A stream,river or another body of water.
The horizon
a river
It usually stands for rivers or borders, depends which map you're looking at.
A wavy blue line on a map usually indicates water. I could indicate a river, canal, or any type of waterway.
Usually represent a stream, river, or other body's of water.
Water represents a blue line on a map.