I have very little experience with Unity, but I’ve experimented with walking around a landscape with a first person character.
What I want to make would look a bit like this:
You’d be able to collide with these objects, so they could block your way, or you could stand on top of them, and if you were to step or jump off of the sinking platform, it would stop sinking. The platform would eventually reach the ground, and stop.
Thanks for any help or advice!