Close it and fill the tub with about an inch ... but if you cover the drain and overflow hole, it may create enough mechanical force to push the clog out of the way. Again, maybe.
If water rises as you shower, rather than running down the drain, you likely have a clog. Here are 5 tried-and-true methods you'll need to unclog a shower drain.
Watch this video for chemical-free ways to fix a clogged drain. How to unclog a bathtub drain full of hair The easiest way to unclog a drain full of hair is by using an auger or a drain snake.