Immobilizer keys, Transponder keys, Accessory keys.

Some modern car keys don't like swimming.

Modern cars come with immobilizer car keys that have made things more difficult for thieves. Thieves  are now on the lookout for any keys that are lying about.  I remember when taking the car to the beach was not a problem, you just threaded the key onto  the cord of your togs and went in the water. Now what do you do if you are warned that your key contains delicate electronics that must be kept dry.  I doubt that you will enjoy your day  with the thought that  a thief may having the time of his/her life wandering around the car park pressing your remote and waiting for your car to signal back that it is ready to be stolen. Think how easy this, they keep the key in their pocket, keep pressing and when a car responds they just walk over with a carefree look and get in.

Some solutions.

Try to buy a special waterproof immobilizer only key that you will only use when you go swimming. It will not have the remote door control as this needs buttons  which are a source of leaks and you may not be able to set/unset the alarm with it.

You can get special waterproof bags/containers that will hold your keys and perhaps your phone.  They could be a bit awkward and may leak.

Have a key cut that will manually open the car door ( no electronics to get wet ) and keep it on you and keep the key that starts the car in the car. Thieves may break into your car and find the key (they know a lot about hiding keys). You may not be able to set/unset the alarm with the "dumb"door key.  You can get a small  car safe, perhaps with a combination lock and lock the starting key in it and  if you are really paranoid you could also have a secret cut out switch fitted.

Come to think of it a small car safe could hold your other valuables.

It pays to study the owners manual and ask around.  Start with the dealer then try to find out what locksmith the dealer uses and ask them. When I did I received some conflicting advice. 

My Honda came with keys that can be taken apart to change the battery and it contains two separate electronic circuits.

The circled box section contains the transponder chip for the engine immobilizer.  I think it is like the chips that they put into animals and it should run forever and may well be waterproof. The clear plastic block with the buttons is the remote door lock control. It clips apart to change the battery and it is certainly not water proof.   It is fortunate that on my particular car  the remote door control plays no part in the engine immobilizer function. Some cars come with the remote door lock control packaged separately to the key that starts the car so you can just leave the remote in the car.  Perhaps you have a key with a faulty remote and can experiment with some silicone sealer to make your swimming key.

I had a "dumb" (no electronics) key made not particularly to use for swimming but as an accessory key (see below). It would be useful for swimming as I could hide the real key in the car and lock the door which sets the alarm.

Alarm setting and unsetting.

Reading the manual revealed that my standard factory alarm is set 15 seconds after the car is locked  using the remote or by using a key in the drivers door and it is unset by opening the door with a key or remote.  The good news is that the new key worked fine to enter the car and thus unset the alarm  and of course it would not start the car. 

Accessory key.

My old 1981 Toyota Crown like most if not all cars of that era had an  ACCESSORY KEY  that  would not turn in the lock past the Acc. position and thus would not start the car. I found this handy and  my wife did to. She likes to  listen to the radio and I often leave her in the car when  I  go to do some business. She is happier sitting in the passenger seat knowing that she can not taken for an unwanted ride. The new "dumb" key acts just like an accessory key only better because it can be momentarily rotated to the ignition position to adjust the windows.

I saw this device at a hardware store. It can be installed on a wall for house keys but I can't see why it could not be fixed in the car and used to secure the key that starts the engine. It looks big enough to hold credit cards and some money. Do not advertise that you have installed a device like this as given time to prepare all devices can be defeated in some way. If an unprepared theif comes across it you should be ok. There is a similar device that has push buttons.

Sorting out this swimming problem on a new car takes some effort and each car is different. I hope the above gave you some background information that is helpful