In all seriousness, if you are concerned you can buy a mast float that is normally attached to the top of a sailing dinghy. I’ve have used one when the wind picks up and the mast will take in water if it capsizes.

I think there are ones you can fold up and then blow up if you need to. For that matter any study inflatable bag will work. You will have to figure how much buoyancy you need. Maybe use a surf leash to keep the bike close when you’re in the water.

As others have said, you’ll have more important things to worry about, but...

John