I got some fabric printed up by Spoonflower and embroidered the waves on with chain stitch in standard embroidery floss and Rowan knitting cotton for the thicker lines.
(Here's a closeup- the whole thing measures 18"/45cm square and has about 50-60m of embroidery on it)
I added islands on, stuffed them to create a relief effect, and then mounted the fabric onto a wooden frame. (Sorry this one was on the floor- it was hard to get enough distance to fit the whole thing in with a 50mm lens, and my 28mm lens distorts the lines too much)
On a table to show the relief a little better.