Using mixes of SG (COG)+ UMB +Tch of DP+tch Black, and starting in upper right corner with horizontal strokes, begin filling in water area (going around the land area). Get lighter as you come to the front of your painting, by leaving out the DP & Black and then get lighter still, adding some yellow ocher to the Sap or Chrome Oxide toward the very front.
Shadow color:
Take some of your very darkest mix (green+ UMB+DP+tch Black) & add shadows under the land and under the swans & lily pads. Allow to blend into the surrounding water.