The flotation process in seawater is highly complex and multifaceted, wherein the chemistry is very different to that of pure water. The high saline environment compresses the electrical double layers resulting in (i) enhancement of the floatability for surfaces that are already hydrophobic; (ii) mitigation of the slime coatings; (iii) increase of the entrainment; (iv) reduction of the bubbles size; and (v) better froths stability. In parallel, the secondary ions present in seawater cause a colloidal precipitation and a strong buffering effect, which difficult the operation at high alkaline condition. The objective of this review is to present a summary of the current knowledge on the subject of seawater flotation processes, highlighting the copper sulphide ores flotation. This review includes a description of the underlying flotation mechanisms affected by the presence of saline water and seawater, as well as a more practical description of industrial flotation operations.