"One of the boys who helps out here put a blanket on him and took him down to the Ranfurly vet who put his dislocated hip back in and put him in a cast.
"They called Jude and said 'we've done all we can and he's comfortable'. He died a few hours later.''
The dog was a "great judge of character'', guiding only people who were "worth taking'', he said.
"If they were heading down to the lake he'd bark and he'd bark and he'd head them on to the walking track and take them along [down to the lake] .''
The last of a litter, he was bought from a local farm girl at 5 weeks old.
Mrs Kavanagh said they would sprinkle some of his ashes around the lake and place a plaque in the beer garden outside the hotel.
"He was wonderful with kids, wonderful with everybody. I can't get over it.''
As well as guiding, Jack also loved a game of pool.
"He used to pinch the white ball off the table. People would want to play and they'd see it in his mouth.''
He almost never took scraps off people and came home to be fed, Mrs Kavanagh said.
"Except there was one time when he wasn't even a year old, I had a ham on the bone to take out to the cooler, and the next thing everyone's laughing, Jack was off with it down the lake.''
Locals knew the dog well and holidaymakers would still ask about him, she said.