The understanding of biointerfaces in contact with seawater is crucially important in tackling the problems of marine biofouling. Such biointerfaces involve the bioadhesives used by marine organisms to attach temporary or permanently to the surfaces immersed in water. The aim of this Thesis is to address a particular problem, i.e. barnacle adhesion, to the biointerface and the corresponding fouling process. We try to understand the first steps of the fouling process of this species, and help to set up design criteria for surfaces to suppress, or prevent, corresponding biofouling. The focus in this Thesis is on AFM-based nanoscale characterization of marine bio-interfaces created by barnacle cyprid larva during surface exploration. The application of AFM has the advantages of first visualizing the fouling interface (also in situ), and to measure its nano-scale properties featuring bioadhesives and adhesives in native environments. The morphology and nanomechanical properties of the cyprid temporary adhesive - “footprints” deposited on the surfaces were extensively studied. In addition, bio-interfaces created on surfaces with different wettabilities were used to investigate the settlement behavior of cyprid larvae in laboratory settlement assays and marine field tests. In-depth investigations of barnacle adhesive properties were performed by in situ monitoring of the enzymatic proteolysis degradation of footprint and the in situ curing process of cyprid permanent cement.