If you're going to buy them at the gate, your discount choices are limited. You can get a discount with a AAA card or $CDN at par (if it's offered). However, you can go to
www.seaworld.com and buy tickets at a pretty good discount. You print them out from your home printer and go directly to the gate. Also try places like
www.ticketmania.com who will deliver your tickets to your hotel at no charge.