I found a good website that describes this topic well: https://phoenixenglishlang.com/s-tongue-twisters/

One of the most famous tongue twisters is: "She sells seashells on the seashore. The shells she sells are surely seashells. So, if she sells shells on the seashore, I'm sure she sells seashore shells." I think it's quite difficult! There are video versions of this on Youtube, that repeat the phrase several times slowly to help people practice it.