Bright red with small dark spots it is one of the most striking echinoderms in New Zealand waters. The red sea star stands out against the grey rock and brown kelp. A flash of colour in the dim light. The spots are arranged in regular rows along each arm. This gives the star a patterned almost decorative appearance. Visibility is high. Contrast is sharp. The reef provides the background. The star provides the signal. Warm northern waters are its home. The red sea star lives only in the northern North Island. From Northland to the Bay of Plenty. It reaches its southern limit here. Further south the water is too cold. It is a tropical species that has extended into temperate waters. A reminder that New Zealand sits at the convergence of warm and cold currents. Range is restricted. Adaptation is specific. Survival depends on warmth. Slow and deliberate it moves across the reef. The red sea star crawls on hundreds of tube feet. Each one is tipped with a suction cup. It feeds on sponges and small encrusting animals. It uses its tube feet to pull food towards its mouth. The mouth is on the underside of the disc. It is surrounded by five jaws. Movement is gradual. Consumption is steady. The process is efficient. Rocky reefs and kelp forests provide its preferred habitat. The red sea star lives from five to thirty metres depth. It occurs on vertical walls and overhangs where sponges are common. It prefers clear warm water with good visibility. When the water is murky it retreats to deeper areas. Clarity is preferred. Turbidity is avoided. The choice is environmental. Its bright colour may be a warning. Many brightly coloured sea stars are toxic. Their pigments signal danger to predators. The red sea star is not known to be toxic. But its colour may still deter predators. A fish that has never eaten a red sea star does not know whether it is safe. Caution is a good strategy. Uncertainty protects. Knowledge is not required. The bluff works. Climate change may affect its range. As the ocean warms tropical species like the red sea star may expand southward. New Zealand waters are already seeing an influx of warm-water species. The red sea star may become more common in the Bay of Plenty. It may even reach the northern South Island. Or it may retreat northward if the water becomes too warm. No one knows. Prediction is difficult. Variation is certain. The future is open. For now the red sea star remains a northern speciality. Divers who visit the Poor Knights Islands or the Bay of Islands know to look for it. They look on the walls and overhangs. It is a small star. Only eight to twelve centimetres across. But its bright red colour makes it easy to spot. It is one of the treasures of New Zealand's warm northern reefs. Observation is rewarded. Discovery is likely. The dive is worthwhile.