Described herein is the synthesis of adhesive complex coacervates and their use thereof. The adhesive complex coacervates are produced by reacting (a) at least one poly anion comprising a plurality of activated ester groups, and (b) at least one polycation comprising a plurality of nucleophilic groups, wherein the nucleophilic groups react with the activated ester groups to produce a new oovalent bond between the polycation and the polyanion. The adhesive complex coacervates described herein have low interfacial tension with water and wettable substrates. When applied to a wet substrate they spread over the interface rather than beading up. The adhesive complex coacervates have numerous biological applications as bioadhesives and drug delivery devices. In particular, the adhesive complex coacervates described herein are particularly useful in wet or underwater applications and situations where water is present such as, for example, physiological conditions.