That 4th wire is only for another ground. If your dryer is 220 like most electric dryers, the outlet should already have a 12/3 wire in the wall behind your current outlet. I.E. You should have a bare Copper (ground), a White wire (called a common, but is connected to the same bar as the ground wire), a Black wire that is 110 Volts that is connected to one leg of a double breaker and a Red wire that is also 110 Volts and is connected to the other portion of the double breaker.

I doubt if you really need an electrician to run a new wire. I bet the extra wire you need is already behind your existing outlet. To check it, turn off the breaker that feeds it, just to be safe use a meter to test it to make sure it's dead. Loosen the outlet and pull it out enough with the current wires still connected and look at the romex that is feeding it to see if there is a 4th wire available for you to use.

BTW, beautiful place! I'm also moving closer to the water. Vada point ramp will be about 150 yds away as the crow flies and it has it's share of scorpions and tarantulas.