Yesterday I picked up my new car (A4 2.0T FSI quattro AVANT) and this morning i put my board in the back ready to go for a surf at Burliegh Heads and I don't know how to lock the car. The key splits from the computer bit so I can tie the metal bit to my shorts but if I leave the computer bit in the car can't anyone open it, press the start button and proudly drive off?

Do I need a waterproof housing to hold the Key if I want to go surfing?

Please help?