I think you answered your question already. It does appear to be a terrestrial grass. Pretty cool though.
Awesome. Just FYI, if you want to propagate it and stick some in the other driftwood cracks, you can split the crown (it looks to me like this type of grass would be a great candidate for splitting) . Let it get some more growth , then gently pull or carefully cut the crown into a couple or more plants (each with roots and shoots) . Just looking at your pics, I see 4 viable plants there.I have no idea how to propogate the thing, and I don't want to get rid of it....so, I'm stuck.