Character/Avatar on XR Rig help

I've only dabbled with PC Games with Unity and am trying VR Development out. I've made a decent environment with GAIA and have a bunch of objects that I can interact with around environment. My biggest challenge right now is I cant figure out how to add a char/avatar or even a cube to a XR Rig so as I walk around there is something moving around besides a pair of VR hands. The XR Rig does have a Rigidbody attached to it so I know objects in environment can hit me and move me but its only if it hits hands. I want a BODY!

Also has anyone been able to find a good water prefab or anything? I can't seem to find one.. what if I wanted to go swimming in my VR App