When you get off the ferry at Aberdeen, go to the right, pop down through the tunnel and when you come up (to the left), cross the bus station. Immediately and right next to the fruit shop and a bank (DBS?) there are two mini buses. One of those will take you to Cyberport. they leave every few minutes.
A word of caution, if you wait at the bus stop at the top of the tunnel, near to the ferry, the buses will almost always be full.
This is the way parent/carers go to Kennedy school as the buses go straight past there. Happy travelling!
