a large container full of warm salty water, often with a cover on it to make it dark inside, that you float in so that you can relax, or to treat illness or injury 浮箱〔内装温盐水的大容器，通常不透光，人在里面漂浮可以放松、治病或疗伤〕
Examples from the Corpus
flotation tank• The difference between a flotation tank and other relaxation techniques is that other methods require effort on the part of the patient.• All right then, how many of your would like to try a session in a flotation tank?• For the ultimate in relaxation, few treatments can beat the experience of a flotation tank.• Clients wash and shower before entering the flotation tank.