Sheila Laxon, the first female trainer to win the Melbourne Cup, has picked the Lloyd Williams-owned Johannes Vermeer to win this year.

"He'll be fit enough to win," Laxon told AAP.

Laxon was speaking to a crowd on board the Explorer on Sunday, one of four P&O ships that have set sail from Sydney and Brisbane with about 8000 passengers to attend the Melbourne Cup.

She trained Ethereal to win the Caulfield and Melbourne Cups in 2001.

Laxon will be studying the field of 24 horses in more detail closer to Australia's most famous race at 3pm on Tuesday.

She says it is hard to pick a winner based only on the information available such as the horse's breeding, but as a trainer she has found those that respond to her commands seem to know why they are racing.

"Ethereal always knew she was out to win races and she knew where the finish line was and you can't make a horse do that," Laxon said.

"They've got to know to do that."

Laxon has found that quality in a five-year-old mare she is training called Mewstone Rock.

"She can gallop and she's got the mental ability to want to gallop," she said.

"But she also swings one leg out and she hits the ground quite hard, so she'll get the hill training that Ethereal used to get."