Mermaids are blessed with one tail or two, are as happy in freshwater as salt, and boast an ancestry that stretches from the classical world to the present, pre-dating Homer's sirens and which will outlive the blood-thirsty nymphs of Pirates of the Caribbean. The mermaid expresses our reliance on the sea for food and trade and draws on our fear and fascination of the unknown depths. From her roots in Assyrian reliefs and her casting in Medieval bestiaries, she has been carved into churches, painted onto pub signs and Pre-Raphaelite canvases, inked into skin, sketched by Picasso, starred in Hollywood movies and in 21st century graffiti, reclaimed as neither vamp nor victim but as a symbol of womanhood and resistance. Few creatures claim this allure or longevity. Mermaids' culture spans eras, continents, art forms.