The assessment of cosmetic efficacy is rarely performed in studies comparing different concentrations of active compounds. The aim of the present study was to determine the skin hydrating and the skin firming dose-response effects of cosmetic formulations enriched in compounds derived from algae and fish collagen. A series of factors were studied including the type of formulation (cream or serum), the concentration in active ingredients, the effect of repetitive applications, as well as any residual effect of the formulations after stopping their applications. The serum enriched in marine compounds showed a better moisturizing effect in short term. The cream appeared more active later, particularly following repeat applications. A sustained tensor (firming) effect was observed during treatment with both the lotion and the cream. However, no remnant firming effect was perceived after stopping treatment.