I have been to Ocean Park twice, with the most recent being December 2010. I went on a weekday (can't remember exactly what day), and the park was busy. However the lines for all attractions were short, due to most of the people in the park being locals (particularly seniors) who spent the majority of their time taking photos and watching shows. In addition the attractions are spread out helping the park manage crowds, although some sections and walkways can become packed. I don't think you will have any problems in seeing all the rides/attractions/shows.
However, here are some touring tips:
- To save time pre purchase your ticket from any 7-Eleven store
- Arrive at the park at opening time
- Proceed to the "Summit" area by train/cable car and tackle the big thrill rides first (Hair Raiser, The Rapids, Abyss, Dragon etc)
- Ride the other major rides (Mine Train, Flume) at your leisure
- Arrive at least 15-20 minutes early for shows to secure a good seat
- Take you time with the amazing animal exhibits, in particular the huge Atoll Reef
- The cable car is a must for the awesome view
- You can still ride the the cable car back down the mountain after the park "closes", so keep this in mind
- Be prepared to do a lot of walking!
I hope this helps and that you enjoy the park!