Foster paints wilderness landscapes, often trekking to remote locales where he works en plein air. WaterMarks is a catalog of a 2003 exhibition of paintings by Foster which was curated by the Royal Albert Memorial Museum in England and traveled to museums and galleries across America. The common theme uniting these paintings is water, and to depict his subject in its many forms Foster voyaged to the icebergs of Greenland, the rivers of Honduras and Colorado, the prismatic pools of Yellowstone, the swamps of Georgia, the waterfalls of Guyana, and more. He even drew sketches underwater in the reefs off the Maldives.