The underwater adhesive materials inspired by marine mussels have been a research hotspot. As is known to all, interface adhesion properties, mechanical properties, rapid response properties are important indicators for the application of underwater adhesive materials. In this study, we report that Poly(N-(3,4-Dihydroxyphenethyl) methacrylamide) (PDMA), a simple dopamine-based homopolymer, replaces complex binary or multiple copolymers as an underwater adhesive material. The influence factors of PDMA were investigated by universal tensile dynamometer, water contact angle tester, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared reflection (FTIR). Meanwhile, the underwater self-assembly performance of PDMA was performed. Compared with the air group, there are more phenolic hydroxyl groups on the surface of the adhesive in the underwater group, and the adhesive performance is better. In summary, PDMA can be regarded as an alternative substitution material for underwater adhesives.