Seabed ground can flow markedly owing to diverse external loading such as earthquake and tsunami. Recent sonar observations and geological surveys report a plenty of the field evidence on submarine mass movements in coastal and offshore areas. However, the dynamics of such submarine mass movements remain largely unclear since on-site observations are formidable if not impossible. Also, conventional studies have focused on the failure conditions of submarine slopes and/or the event deposits surveys, and therefore the submarine sediment flow dynamics that are essential for disaster mitigation and prediction, remain poorly understood. In this report, the author reviews some large-scale submarine mass movements and their consequences highlighting the importance of submarine liquefied flows, and present the theory and analytical framework of the submarine liquefied flow dynamics together with their experimental and field validations. It elucidates the crucial role of the two-phase physics in flow stratification, deceleration and re-deposition as well as in the formation of scarps and terrace in submarine liquefied flows. The developed analytical framework is widely applicable for predicting and assessing the large-scale sediment flows and evaluating their impact and influence on tsunami and the stability of coastal/offshore structures.