Been there.
We arrived on Diamond Princess thinking Christchurch would be closed. There was a full book of the usual tours, including kayaking and punting, and we had an awesome drive through the country to Waimakariri Gorge for a spot of jet boating on the river. Combined with the usual cruise day of not cooking or cleaning, drinks in Crooners and great food, it was a memorable day.
https://www.alpinejetthrills.com/ is open again today.