James Fenimore Cooper
Many of Cooper's writings focused on the American frontier. He often wrote about Native American life especially in his Leatherstocking Tales. He also wrote sea novels as well as the historical novel "History of the Navy of the United States of America".
Mark Twain is well-known for his writing about American life, but not for introducing the sea. He did introduce the Mississippi River. Herman Melville is most widely known for introducing the sea in his novel, Moby D__.