Ooo, spooky ghosts! Well, if your sim has a knowledge aspiration he/she would just love to see one. I would... the problem is, the way this game has desgned the ghosts, you need to squint to look at them. There is a way to make the ghost look perfectly human, but floating.

1. Press Ctr+shft+c to bring up the cheat code entering box
2. Type in "move_objects on" (No quotations) and go to the building or furniting tool.
3. You will now be able to pick up virtually anything.
4.Grab the ghost and move him/her where ever you want, but you NEED to move him/her.
5. Go back to playing and unpause if the game was paused and you should see a perfectly coloured, opague ghost.

(I'm not sure if ghosts that drowned stop dropping water after doing this but you can give it a shot)