I'd suggest trying a plunger. It may not work, but it might, and is
quick and easy. Fill tub, blocking drain if necessary. Block
overflow with duct tape, or stuff wet rag into it. Unblock main
drain, put plunger over it, then pull plunger with short, sharp
strokes for a minute or two, alterenating pulling and pushing, really,
but more pulling. I've cleared a few like this, but wear boots if you
don't like standing in dirty water, because you will be..