Niskin bottles are specialized devices used in oceanography to collect water samples from various depths in the ocean. They are designed to close at specific depths, allowing researchers to capture water without contamination. The bottles are typically made of durable materials and can hold several liters of water. These bottles are often deployed from research vessels during scientific expeditions. When a Niskin bottle is triggered, it seals the water inside, preserving its chemical and biological properties for analysis. This makes them essential tools for studying marine environments and understanding the health of our oceans, including the impacts of climate change and pollution.