I got a voucher a few years ago to swim with the Dolphins at Sea World on the Gold Coast. I must admit I was a bit apprehensive but had the most amazing day.
The instructor was great and swimming with the dolphins was a dream come true. Your not allowed to hang off there fin or swim along side them anymore but we were given goggles to wear so we could watch them do trips whilst wading in the water.
Got a cuddle and picture at the end and left very happy!
As for the park itself it is a little run down but I do believe they are doing some ongoing renovations to it. The underwater aquarium is great and the seal show is really good too.
You can get the 3 park pass which is SUPER great value so I would highly recommend that.
Enjoy the Gold Coast! :)