About an hour. You have to go on a ride first. It's a simulator. Do the walkthru version, you see the same movie, and won't get sick, plus the lines are shorter.
If you really wanna see everything about the polar bear exhibit, do the Polar Bear tour. You'll go behind the exhibit and see the holding areas, how they feed them, and then you board a bus that takes you to the penguin holding area and you pet them.
Sign up for this tour as you walk into the park. It's usually done in the afternoon around 2pm. It's not that expensive, and well worth it.