The electrical wiring on a ocean or fresh water boat should be wire to the same standards to prevent corrosion and electrical problems. River boat manufactures almost never protect the wiring from corrosion. If salt water get on a unprotected terminal strip or wiring if not seals it will corrode. Most boats that are used in fresh water don't have anodes and if they do there are not zincs that is needs to protect a boat in salt water.

If a boat is only going to be in salt water for a day or two you don't need anodes if longer and several time a year you might consider adding zincs especially if you see corrosion. Don't forget the Engines also may needs protection.

The trailer should also have it wiring seal before going into salt water and everything wash down with fresh water including the brakes as soon as possible.