Waterhouse, speaking while having her nails done at a Melbourne spa on Monday, said she had been up since 2.10am attending to her horses at Flemington. She described Sir Delius, a six-year-old gelding, as going "very well" and "very happy".
"I have got him very fit so now it is just a matter of letting the days pass until the Cox Plate," Waterhouse said.
Sir Delius was scratched from last year's Cox Plate after stewards determined a pre-race scan showed him to be at a heightened risk of injury. Waterhouse is training the horse in partnership with Adrian Bott.
The Cox Plate is being run at Flemington this year while Moonee Valley is being rebuilt. Waterhouse's father Tommy Smith won the race with Redcraze, Tulloch, Gunsynd, three times with Kingston Town and Red Anchor.
Waterhouse, named one of 100 national living treasures in 1997, has trained great horses including Pierro, Melbourne Cup winner Fiorente, and Alligator Blood. She has placed horses in the Cox Plate before but never won.
"I would love to be able to win it once, and hopefully many more times before I am pushing up daisies, but you have got to have the horses and I have definitely got the horse to be extremely competitive on Saturday," Waterhouse said.
Waterhouse, who appeared in 'Doctor Who' in 1978 and had a modelling career, is also active on TikTok and Instagram. Her husband Rob said she remembers horses from a decade ago better than she remembers people.
"Nothing dents my confidence," Waterhouse said, when asked about the challenge of the hot pace set by Ciaron Maher's pair Land Legend and Light Infantry Man. nThe race will be run at about 5pm on Saturday at Flemington.