If where you park your car when you go surfing has good internet connection, and if you have an Apple Watch Series 2, you could leave your key at home. As long as you leave your iPhone in the car, you can use the Remote S app to lock and unlock the door with your Watch. And Watch 2 is waterproof so hopefully safe for surfing.
This is what I do when I go jogging. No need to carry a key with me (in case it rains). Just make sure you have Internet connection there before embarking on this endeavor.
I don't know if you could duplicate this process with an Android phone and watch.