Ghost shrimp are sometimes acclimated to SW and fed live to SW fish. I don't know if they can live a long time in SW, but they can live for a while at least (even though they're generally FW - there are actually multiple species of shrimp that are sold as ghosts). I once saw (at the LFS) a few ghost shrimp swimming around in a tank as feeders for a small octopus. It was pretty cool - I watched as he snuck up and caught one.