You live in Florida. Snakes are everywhere. This is probably not the first in your coach and it will probably not be the last. If the coach is parked anywhere near a wooded area, which are everywhere, the snakes like to find a nice dark space to stay warm. They like warm, but not too warm. Put a 150 watt incandescent bulb in your wet compartment and leave the door open enough for the snake to get out. He won't like the heat or the light.
Then the best you can do is to try to insure that all possible holes are plugged up, including the one your power cord comes out to hook up to shore power.