[math-fun] A different kind of polyhedral "torus"

I believe there's a way to take eight unit cubes and join them edge to edge (so that each cube has two edges that are joined to edges of two neighboring cubes) so that (1) the whole chain of cubes can be collapsed into a 2-by-2-by-2 cube, and (2) the chain of cubes, when pulled open, admits a swimming-through-itself motion. Does such a thing exist? (I think I've played with such a thing but I'm not 100% sure.) Are there photos and/or videos on the web? Jim Propp