Hey, i was studying this tutorial of

http://www.cartographersguild.com/tu...l-rpg-map.html


however, i was stuck at the -----" Post 6: Create the sea. (in the beginning...)" part

because my pic was 2592 x 4768, the size was too big to use "Gaussian Blur", to create the ocean effect

anyone has any idea to proceed my "sea designing" part? or any other way to achieve the same effect as the tutorial thread has shown ?