Deep ocean water (DOW) is seawater found at depth of several-hundred meters or lower, and has attracted special interest as one of the renewable resources with great potential, since large amount of cold and stable DOW is renewed in thermohaline circulation such as the great global conveyer. DOW has also been focused as important resource for enhancing marine primary production because DOW contains much inorganic nutrients, such as nitrogen, phosphorus, and silica. In this chapter, we describe fundamental features of DOW and discuss the importance of utilization of DOW, from the viewpoint of sustainability of global environment. We also introduce several technologies of DOW utilizations, such as ocean thermal energy conversion (OTEC), air conditioning, fisheries application, agricultural application, freshwater production, and so forth. Finally, we propose a multipurpose DOW complex float, which generates electric power, freshwater, rare metal and fish ground from only DOW and surface seawater as a sustainable infrastructure.