We have been asked how to, so we tested something and it worked. However it's not a great way to do things so it's not exactly a 'tutorial'. And remember not to save your game after you took those pictures, you would have a lot of errors causing your game to malfunction.
Here is the result, using a couple pose from the Bath Time Fun pose pack.
To start, you will want to prepare your characters by having them take the pose in advance. You will need at least an extra random character that you do not need in your scene/picture, maybe more depending how many poses you want to use.
For this example we will start with our couple, posing near the bathtub, and the woman on the right side we are going to use to turn the tap on and fill the bath with water:
If the sim needs privacy just momentarily place the posed characters in another room close by.
Have the sim turn the tap, fill the bath with water and sit in.
Now that the sim is in the bath, pause the game, go into buy mode and try to move the sim. It will not work, but press the delete button. It will cause the sim to desappear with the water still in.
Do not unpause the game! Instead place the posed sims in the tub, go back to live mode and take your picture.
If you unpause, the water will disappear in about 2 seconds and you will end up like this:
So if you need to do a photoshoot for your story that includes more than one pose, make sure you invite a lot of people in your active family, take all the pictures you need and then go back to a previous save to make sure you won't be bugging your game with the missing sims.
Another pose for the bath from the Bath Time! pack made by SeeMyu (used to be called SIMul8rReviews)
Here are more poses related to bathing presented on this blog.