how to get to ocean park from royal plaza hotel without passing the tunnel?

If you don't want to take subways, you can take bus no. 1A at Heep Woh Primary School and get to Nelson Street Mong Kok. Then transfer to bus no.171 to Aberdeen Tunnel Toll Plaza.
The wholeway takes around 50 mins. And the ticket fare is 16.9 HKD per person.
After arriving, walk south around 220 yards to arrive at the main gate of the park.