Easiest way to add buoyancy

Hi there, ive been making a simple fishing game and i have a nice water material however im trying to have the bobber for the fishing line float atop the water however im not sure how i can do this. It doesn’t need to be the most accurate thing in the world i would just like a little bit of motion similar too the waves. I have seen a few tutorials by someone on youtube however it requires the use of their own tutorials material. Any help would be appreciated thanks.