Water stagnation and submergence are major factors in rice growing. Water stagnation and submergence happen as a result of excessive rainfall or flash floods. The duration of submergence can last several weeks, and the level of water may be as high as 100 cm. This impacts rice yields. This book analyzes different aspects, viz., morphology, physiology, biochemistry and genetics, and reviews the suitability of different varieties for better sustainability and reduction of yield loss. It also reviews the different types of floods, and studies biological changes in indigenous and recently developed rice varieties. There are seven chapters: Introduction, History of floods, Diversity of submergence, Adoptive morphology, Physiological aspects, Molecular and genetic aspects, and Yield and yield-gaps. It is comprehensive with scientific dogma, findings and reasonings for students at universities and researchers.