Dissolved molecular oxygen in solution depolarizes muonium because ground-state molecular oxygen has triplet electrons and is paramagnetic. People normally remove them from sample solution as nuisance, but oxygen-muonium interaction in liquid water may be physically interesting system because liquid water is a strongly correlated, frustrated system, and microscopic diffusion and interaction mechanism between solute molecules are totally different from gas. We recently found that the muonium relaxation can be observed in air-saturated water, which led to a discovery of saturation of relaxation rate in high oxygen concentration. We propose to investigate this anomalous behavior by changing the temperature and oxygen concentration, and understand the interaction mechanism between oxygen and muonium.