is to turn off the breaker at the pedestal on the dock, then unplug the shore power cord from the boat. My thought was not about arcing (thanks for that info btw) but me possibly dropping a hot cord into the water or someone kicking it off the dock into the water while we are out.

Now, where we are now, on the hard, the main breaker on the AC panel has been left on as well as the outlet breaker so yes, the loads are on. However, this "shore power cord" is actually a 20amp rated extension cord that plugs into a standard 110 outlet box. It remains plugged into the shore power inlet on the boat all winter, actually shrink wrapped in place. The 3-prong plug gets plugged into an outlet on one of the picnic shelters that is left on year round for just that purpose.