I have used this Radio Shack AC wireless remote to turn on my camp lights when I near the driveway. I have left it outside in all kinds of weather for several years and it has never failed.
You can get similar models off the shelf at most Home Depots & Lowes.
For $15 you can't go wrong, and if you place it correctly with a good line of sight you will get several hundred feet of range over the water.
Check it out
HERE!