Yes, but I think the idea is that it won't tip.

edit: I'm more of a spirits guy, but I always thought rocking whiskey glasses were really cool. Apparently they were designed to house liquor or wine without spilling on a sailboat. I even have a decanter that goes with a similar tumbler set, though I have no idea where that is; still, always liked them. Obviously the sand temperature isn't an issue with them, though.