I think he’s referring to switching to an electric over hydraulic actuator, not electric brakes like you would find on a travel trailer, those wouldn’t last a month in the salt.
To answer your question, yes you can reuse your existing drums, but if you want to eventually switch over to disk brakes then it would require a 1600psi actuator vs a 1000psi actuator. The disk setups are substantially more corrosion resistant and offer superior braking performance, I would never go back to a drum brake setup, especially in the salt water conditions.