We did the Cat last month, so had to try the Duck (just didn't take any photos of the outside (look it up online if you have no idea what I'm on about!). Cassie (tour guide) was great (and asked for a plug!)
On land - under Bluff Hill
And on the sea - was a great experience, and got great historical info about Napier - even things I didn't know after spending so much of my life there!
Then we jumped on a bus to do a winery and brewery tour (the kids didn't taste the wine, but did get to taste the ginger beer and apple cider (the non-alcoholic versions!) at the Filter Room 
And the last stop was long and social - the girls took photos of each other (among other things!)
Well recommended, even for locals.