Hypersaline environments occur naturally worldwide in arid and semiarid regions or in artificial areas where the discharge of highly saline wastewaters, such as produced water (PW) from oil and gas industrial setups, has concentrated salt (NaCl). Halophytes can tolerate high NaCl concentrations by adopting ion extrusion and inclusion mechanisms at cell, tissue, and organ levels; however, there is still much that is not clear in the response of these plants to salinity and completely unknown issues in hypersaline conditions. Mechanisms of tolerance to saline and hypersaline conditions of four different halophytes (Suaeda fruticosa(L.) Forssk,Halocnemum strobilaceum(Pall.) M. Bieb.,Juncus maritimusLam. andPhragmites australis(Cav.) Trin. ex Steudel) were assessed by analysing growth, chlorophyll fluorescence and photosynthetic pigment parameters, nutrients, and sodium (Na) uptake and distribution in different organs. Plants were exposed to high saline (257 mM or 15 g L−1NaCl) and extremely high or hypersaline (514, 856, and 1712 mM or 30, 50, and 100 g L−1NaCl) salt concentrations in a hydroponic floating culture system for 28 days. The two dicotyledonousS.fruticosaandH.strobilaceumresulted in greater tolerance to hypersaline concentrations than the two monocotyledonous speciesJ. maritimusandP. australis. Plant biomass and major cation (K, Ca, and Mg) distributions among above- and below-ground organs evidenced the osmoprotectant roles of K in the leaves ofS.fruticosa, and of Ca and Mg in the leaves and stem ofH.strobilaceum. InJ.maritimusandP.australisthe rhizome modulated the reduced uptake and translocation of nutrients and Na to shoot with increasing salinity levels.S.fruticosaandH.strobilaceumabsorbed and accumulated elevated Na amounts in the aerial parts at all the NaCl doses tested, with high bioaccumulation (from 0.5 to 8.3) and translocation (1.7–16.2) factors. In the two monocotyledons, Na increased in the root and rhizome with the increasing concentration of external NaCl, dramatically reducing the growth inJ. maritimusat both 50 and 100 g L−1NaCl and compromising the survival ofP. australisat 30 g L−1NaCl and over after two weeks of treatment.