My master bath and regular use bathroom share a wall.

My husband turned on the master-shower and noticed the water wasn't draining like normal so he took the hair and gunk that he could reach and pulled it out but the water still wasn't draining right. He grabbed the plunger to see if he could pull anything up and I heard water in the regular use bathtub! When I looked in the bathtub it was filling up with wather that had dirt & SAND in it! I ran into the master bath and made my hubby stop. We then flushed the master bath toilet to see what would happen and all of a sudden the master shower and regular use bathtub SLOWLY emptied!

What the heck is happening??

BTW: the dirty water didn't smell bad like sewer water.

You had a blockage in toilet line. You now have a partial blockage in toilet line. Sounds like someone cleaned the aquarium in the tub or dumped kitty litter down the toilet. If problem continues you will have to snake the tub or shower line.

Could Harold be correct? Could someone have cleaned the aquarium in the tub or dumped kitty litter down the toilet.
If you have to snake you can snake from one of two places.
1) You can pull the master bath toilet **OR**
2) Snake from the master bath lavatory roof vent.
Good luck, Tom