Newcastle is another place with a great harbour so you should make sure that if you've got an hour or two to spare you wander along the harbour. It's a quiet harbour but it's nice all the same. You could grab lunch and just chill out or you could hire a boat and get out on the harbour with friends. It's really up to you how you enjoy Newcastle Harbour.
If you decide to go for a walk it's just a few hundred metres and it's really close to the city. You can basically enjoy this all year round and it's something everyone will enjoy.
I especially like doing this on a weekday, but it doesn't matter when so long as the weather is great, then you won't need to worry about the cool ocean breeze.