Koombana Beach is a modest beach on Koombana Bay. This has a view of the port. It is a protected beach with no surf. There are wild dolphins in Koombana Bay, which you may be lucky enough to see close to the beach. The best time to go is in the morning.
The Dolphin Discovery Centre is on Koombana Beach. There is not much to see inside the centre, only a few display boards with less dolphin information then you could find out in a minute on wikipedia. You may want to check if there are any dolphins around on the beach before you pay the admission, otherwise you get very little for your money. There are no captive dolphins at the centre. They also run trips out to where the dolphins are, but these need to be booked in advance.