Nature has developed protein‐based adhesives whose underwater performance has attracted much research attention over the last few decades. The adhesive proteins are rich in catechols combined with amphiphilic and ionic features. This combination of features constitutes a supramolecular toolbox, to provide stimuli‐responsive processing of the adhesive, to secure strong adhesion to a variety of surfaces, and to control the cohesive properties of the material. Here, the versatile interactions used in adhesives secreted by sandcastle worms and mussels are explored. These biological principles are then put in a broader perspective, and synthetic adhesive systems that are based on different types of supramolecular interactions are summarized. The variety and combinations of interactions that can be used in the design of new adhesive systems are highlighted. The adhesive secretions of marine animals, such as sandcastle worms and mussels, combine covalent and noncovalent interactions to afford strong underwater adhesion. These marine animals are taken as a basis for inspiration and discussion on possible interactions that can be used to control the adhesive and cohesive performance of synthetically designed adhesives.