If the leak is comming from the OUTSIDE of the tub them all you need to do it to keep the shower doors, curtains closed.
But how have you identified this.
There are numerous place where you can get a leak in the bathroom from either the supply or the drains or in addtion to people not closing the curtains or spilling water on the floor.
It takes some detective work to ID the source and often that means cutting out the ceiling below.