one suggestion from an interest group which I”m actively involved with is Masters Sports people.
I do rowing and I know that lots of rowers like weekend and week-long breaks.
There are free classifieds on the RowingNZ.kiwi website; contact your local clubs in Picton, Nelson, Blenheim and the Wellington clubs.
Also speak to Kevin Strickland from Swift Coastal boats because if he can rent the boats, you have the location then all the folks have to do is turn up.
Mention my name.
You can also do this for kayak, SUP and other water sports.