With its disc-shaped body, vivid blue colour, intense stare and pursed lips, the blue doctorfish looks like something from a child's drawing. On the seventh coin in the Luminous Marine Life series, it can also change colour with the help of ultraviolet light.

The blue doctorfish gets its name from bony projections on its tail that have a razor-sharp edge not unlike a surgeon’s scalpel. When a rival comes close, the striking yellow ‘scapel’ is extended as a threat to ward off attack, which can lead to nasty cuts being inflicted on the enemy should it fail to heed the warning.

Once young blue doctorfish grow roughly to the size of a 1 euro coin, they begin their life on the seabed. When illuminated with a special light at this stage, they glow an intense greenish colour. The fish play an important role in maintaining the health of coral reefs as they remove algae when feeding, which provides space for coral to flourish. In addition, their droppings fertilise the reef.

Along with the other coins in the Luminous Marine Life series, the Blue Doctorfish is aimed at vividly demonstrating the beauty and vibrancy of the underwater world. To ensure that the marine habitat remains as diverse as on our colourful coins, it must be protected at all costs.

All 12 of the magical sea creatures in the Luminous Marine Life series are shown in silhouette on the coin’s obverse. Air bubbles up between them and a tail fin disappears beneath the waves to the right. On the coin’s reverse, a wide band, reminiscent of an old-fashioned porthole frames an aquatic scene that features a mauve stinger in the centre. An island with palm trees can be seen above the surface of the water. When the coin is illuminated with ultraviolet light, the jellyfish glows and changes colour, so that the light brown of its bell turns blue or red, as does the pinkish purple of its tentacles and oral arms.