Drinking seawater is dangerous because it causes dehydration at the cellular level. Seawater is much saltier than human blood, leading to water flowing out of cells to balance salt concentrations, which can cause salt poisoning. To survive, one must find or create freshwater. Desalination methods, such as thermal and reverse osmosis, are crucial. Thermal desalination uses heat to evaporate water, while reverse osmosis uses pressure to filter salt. Despite their benefits, these methods have drawbacks, including high energy use and waste production. Reverse osmosis is more energy-efficient and less wasteful than thermal methods. Globally, desalination is vital as many regions face water scarcity. Wastewater recycling is another promising solution, as it requires less energy to purify than seawater and provides safe drinking water. In survival situations, collecting rainwater, using thermal desalination, and consuming certain animal fluids can provide hydration.