This letter caters for a performance evaluation of Random Linear Network Coding (RLNC) for broadcasting in underwater acoustic networks by providing a comprehensive numerical analysis, simulation results and experimental results. The RLNC broadcasting scheme is implemented into four acoustic modems deployed on a pier, and into 10 virtual modems in the manufacturer emulator. The results show that, under open sea channel conditions provided by the emulator, the analytical results can be achieved. However, under ultra-shallow water conditions found during tests, the severe time-varying packet loss rate affects the performance of the RLNC broadcasting scheme significantly, and renders the scheme inefficient.¹¹This letter was conducted in the scope of the iFIVE project (POCI-01-0145-FEDER-030500) supported by FEDER, through COMPETE 2020, Algarve 2020, and Fundaç ao para a Ciência e Tecnologia.