Without it, the riverbed is slimy. With it, the stones are clean. The vacuum cleaner of the riverbed. Small, translucent and perpetually busy, the freshwater shrimp scuttles over stones and submerged wood. It grazes on algae and detritus with tiny, comb-like claws. It is a creature of constant motion. Long antennae twitch to sense the current and the approach of danger. A shrimp that never stops working. Rest is not an option. Movement is survival. Individually insignificant, collectively they are a powerhouse of cleaning. They keep river stones free of slime. They keep the water clear. Transparency serves as primary defence. In shallow, sun-dappled water, they are nearly invisible. They appear as nothing more than a shimmer in the current. A shrimp that disappears when looked at. Visibility is low. Safety is high. To the keen eye of a trout or a kōaro, however, they are a moving snack. When threatened, they execute a rapid backward flick of the tail. They shoot away in a blur of motion. This jet-propelled escape leaves predators grasping at water. A shrimp that can teleport. Speed is reactive. Distance is immediate. Survival depends on reflex. Unlike their marine cousins, these shrimp spend their entire lives in fresh water. They never see the sea. They are hardy but particular. Clean, oxygen-rich water is required for survival. If the river turns muddy or stagnant, the wātakataka vanishes first. A shrimp that tells the truth about the water. Purity is a requirement. Pollution is a sentence. The signal is clear. Not currently threatened, freshwater shrimp are the silent sentinels of the stream. Their presence is a small, skittering promise. The water is still pure enough to sustain life. To watch one dart across a sunlit stone is to see a tiny barometer of river health at work. Observation reveals condition. Absence reveals decline. The metric is biological. The data is live. The stone is sunlit. The water is clear. The shrimp darts, translucent and busy. It does not know it is being watched. It does not know it is a sign of health. Awareness is absent. Function is present. The role is defined. The execution is precise. It just cleans. That is all it has ever done. No ambition drives it. No strategy guides it. Instinct dictates action. The algae grows. The shrimp eats. The stone stays clean. The water stays clear. The cycle repeats. It is a quiet victory. No fanfare accompanies it. No celebration marks it. The shrimp simply exists. It continues its work. It maintains its watch. And that seems to be enough. The river flows. The shrimp scuttles. The balance holds. For now. No one told it otherwise.