I used to have cord issues like this, even after replacing components. I tried to keep up with maintenance and procedure such as securing the ring for awhile, then went a better way. Dropping in water is bad, but not required, they don’t last. Here is my overall approach. Renew the connection. If you go to smartplug, recommend getting the full molded cord, not just replacing the end. Next I stopped running more than 15 amps through my cable when I am not present. To do this required updating my inverter charger to a unit where I could set my shore power limit, in my case Victron, but there are other good choices. With a low limit on the cord current, it meant no longer running electric heaters while away. Replacement was a dehumidifier to keep the air fresh without heat circulation.
This is not the only possible approach, better part of the message is that you should think about the overall system as a whole. Burning shore power connections are a common source of boat fires in PNW as many don’t winterize, but try to keep boats semi warm with electric heaters. Cords just wont reliably do it unless everything is perfect and it rarely is so plan accordingly.