From the intertidal zone to the deep sea, these animals occupy every marine habitat. Several different species of sea cucumber live in New Zealand waters. Each is adapted to its own niche. Some are smooth. Others are warty. Some are brown. Others are mottled or striped. Some hide under rocks. Others burrow into the sand. Diversity is high. Adaptation is specific. The group is varied. The most common species, Australostichopus mollis, lives on soft sediment in sheltered bays. But others live on rocky reefs. In seagrass beds. Or on the deep continental slope. Each species has its own shape. Its own colour. Its own way of feeding. Some are deposit feeders. They ingest sediment and extract nutrients. Others are suspension feeders. They catch particles from the water column. Method varies. Function remains. All share the same basic body plan. A sea cucumber is a soft cylinder. It has a mouth at one end. An anus at the other. Tentacles surround the mouth. They are used for feeding. The body wall contains tiny calcitic plates. These are the remnant of the echinoderm skeleton. They can contract their bodies. This makes them small and hard. Or they extend themselves. Becoming long and soft. Flexibility is key. Structure is minimal. When threatened, they defend themselves. Some eject sticky threads to entangle predators. Others eviscerate. They expel their internal organs as a distraction. The organs regenerate within weeks. It is a dramatic defence. But it works. The sea cucumber does not fight. It sacrifices and rebuilds. Loss is temporary. Regrowth is certain. Survival depends on regeneration. The predator is confused. The prey escapes. In Asia, they are a delicacy. Dried sea cucumber, called beche-de-mer, is highly prized in Chinese cuisine. The fishery has collapsed in many parts of the world. Poachers now target New Zealand waters. There is no legal fishery here. But illegal harvesting occurs. The species most at risk are the large, meaty ones. These are the same ones that are most valuable. Demand drives theft. Protection is weak. The threat is real. Climate change threatens all of them. Warming waters affect the seagrass beds. They affect the organic matter that accumulates on the seafloor. Coastal development and dredging destroy soft sediment habitats. The sea cucumber is resilient. But it has limits. Different species will respond differently. Some may thrive. Others may decline. Resilience is tested. Limits are unknown. The future is uncertain. The present is stable. The sea cucumber is not a glamorous animal. It does not have the spines of a kina. Or the arms of a starfish. It is a soft, leathery tube. It processes sediment. It cleans the seafloor. But without it, the seabed would be choked with organic matter. The sea cucumber is the unsung hero of the marine environment. Working quietly in the dark. No fanfare accompanies it. No celebration marks it. It simply exists. It continues its work. It maintains its watch. And that seems to be enough. No one told it otherwise.