Brine pools are highly saline underwater lakes, which are toxic to most marine creatures, due to their high salt content and lack of oxygen.
Yet, a community of uniquely adapted organisms found ways to survive and thrive on the brine pool shore, all interacting on the borders of a toxic pool of brine. Smaller organisms have evolved the ability to convert the methane into energy, supporting a community of bacteria, shrimp and tube worms.
But unadapted animals that are unfortunate enough to delve below the surface will experiencing toxic shock due to the hyper-salinity. Some pools also contain methane and toxic chemicals like hydrogen sulphide. Creatures have been recovered from brine pools with soft tissue still intact, despite having been dead for decades. Crabs that risk their lives in order to feed on the bed of mussels.