Create a comic-book-style illustration titled "Serene Companions," depicting two stylized herons in a tranquil riverscape. The birds should be drawn with intricate patterns on their wings and bodies, rendered in a monochromatic palette with bold outlines. Surrounding them should be rippling water effects and abstract mangrove roots, detailed with crosshatching and shading for a textured look. The dynamic contrast between the bold herons and the subdued background should create a visually engaging image. The background should be transparent, ensuring versatility for apparel printing. Consider adding texture overlays and ensuring high contrast to enhance the overall impact of the illustration.