Drawing a line 10km from a coastline

[690022655Exeter]

Hello, 

For my project I have created a polygon containing a large area of sea, that borders a coastline. i am now interested in creating a line that is 10km offshore, within this polygon. is there a way to draw this line without eyeballing the distance? 

thanks!

[DanPatterson · Accepted solution]

The term is "buffer" and there are many variants,

this is but one

Buffer (Analysis)—ArcGIS Pro | Documentation