Hiya
Found this on Mousesavers.com, hope it helps.
Southwest Airlines Discount
Show your Southwest Airlines Rapid Rewards card at the ticket booth and get 20% off a regular one-day admission. Do the math: this is frequently the best discount available. Limit 4 admissions per card. It is FREE to join Rapid Rewards, and you can get your membership number instantly when you sign up on the Southwest website. Hit the print button when it pops up. SeaWorld will accept a computer printout of your Rapid Rewards card (you dont have to wait for the real one to arrive in the mail). Although this offer disappeared from the Southwest website in late 2009, it is still valid in 2012