With the Floating Body component, you can make objects float realistically in water.
MANUAL ||
DEMO
* works automatically with Sphere, Capsule and box colliders
* Plays well with Unity physics: floating object interact well with other physics
* Automatically works with ragdolls
Advanced water (standard package) will not work with Unity free, but FloatingBody script should work fine with all versions of Unity.
Demo scene uses Unity 4.6 GUI, but again, the Floating Body script should work fine with older versions of Unity too.
Music in the video:
"Dance of the Sugar Plum Fairies" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0
http://creativecommons.org/licenses/by/3.0/
NOTE: Music from video NOT included in package, but can be found at incompetech.com