The rest was Photoshop-specific stuff, indeed. To show you what I mean I just did it with 50% opacity, more than I would recommend and re-upped your map. I'd also - as stated above - drop the thickness of the outline.

Ersi?a-(1).jpg

Maybe you can include a small relief-effect combined with a soft shadow opposed to the lights direction to emphasize the coast a bit more to differentiate the land a bit more from the water. It has been done here, for example (cropped and blank):

Bildschirmfoto 2016-11-03 um 23.12.25.png


Btw, labelling can be hell... my condolences. Did you came up with all names or do you had them already? Just out of interest.

Best wishes,
Steffen