The "pea-green boat" is a whimsical image from the poem "The Owl and the Pussycat" by Edward Lear. In the poem, it serves as a charming vessel that carries the characters, a pussycat and an owl, on their adventures across the sea. The boat's unique color adds to the playful and imaginative tone of the story. This boat symbolizes freedom and exploration, allowing the characters to embark on a journey filled with love and joy. The imagery of the pea-green boat has become iconic, representing the whimsical nature of nonsense literature and the creativity found in children's poetry.