Marine organisms (algae, crustaceans, fish, marine bacteria and microalgae) are rich sources of bioactive molecules — polysaccharides (fucoidan, alginate, carrageenan, chitosan), proteins/peptides (marine collagen, bioactive peptides), pigments (astaxanthin, phycobiliproteins, mycosporine-like amino acids), lipids (omega-3 fatty acids), and secondary metabolites — that are increasingly used as cosmeceutical ingredients. Biotechnology (fermentation, enzymatic hydrolysis, recombinant production, microalgae cultivation, green extraction) enables consistent supply, structural modification and scalable manufacturing of such ingredients. This review summarizes sources, biological activities relevant to skin health (antioxidant, UV-protective, anti-inflammatory, moisturizing, wound-healing, anti-aging), formulation considerations, mechanisms of action, safety and regulatory aspects, and commercial/technical challenges. Key opportunities include engineered peptides, microalgae-derived actives, symbiotic microbiome-targeted products, and sustainable sourcing.