Underwater　optical　images　serve　as　crucial　carriers　and　representations　of　ocean　information.　They　play　a　vital　role　in　the　field　of　marine　exploration.　However,　the　quality　of　images　captured　by　underwater　cameras　often　falls　short　of　the　expected　standards　due　to　the　complex　underwater　environment.　This　limitation　significantly　hampers　the　application　and　advancement　of　intelligent　underwater　image　processing　systems.　Consequently,　underwater　image　enhancement　and　restoration　have　been　attracting　extensive　research　efforts.　In　this　paper,　we　review　the　degradation　mechanisms　and　imaging　models　of　underwater　images,　and　summarize　the　challenges　associated　with　underwater　image　enhancement　and　restoration.　Meanwhile,　we　provide　a　comprehensive　overview　of　the　research　progress　in　underwater　optical　image　enhancement　and　restoration,　and　introduces　the　publicly　available　underwater　image　datasets　and　commonly-used　quality　evaluation　metrics.　Through　extensive　and　systematic　experiments,　the　superiority　and　limitations　of　underwater　image　enhancement　and　restoration　methods　are　further　explored.　Finally,　this　review　discusses　the　existing　issues　in　this　field　and　prospects　future　research　directions.　It　is　hoped　that　this　paper　will　provide　valuable　references　for　future　studies　and　contribute　to　the　advancement　of　research　in　this　domain.　©　2023,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.