I'm new to map making and was looking for inspiration and ideas from the gallery section. Wow! What great maps there. I will probably never be that good, but being half that good would be a giant leap in my skills.

But I noticed many maps that have lines in the oceans, usually radiating out from a point, one or more points, and I was wondering if it is just for looks or do they serve an actual purpose in cartography?

Examples like Diamond's Western Numeria or Max' s Telduria maps have these lines and many others.