Australia's Catholic church has unveiled its secret plan to ensure fine weather for Pope Benedict's planned mid-winter cruise on Sydney Harbour in 2008.

"I have nuns all around this country praying for good weather for that day," Bishop Anthony Fisher, coordinating the Pope's trip in July, told Australian media.

Pope Benedict will make his first visit to Australia as Pope in July for World Youth Day celebrations in Sydney.

Organisers said his official arrival at the World Youth Day celebrations would be by a 13-vessel "boat-a-cade" along Sydney Harbour, prompting Sydney's Daily Telegraph newspaper to run the headline "Pope on the water".

The Telegraph said about 150,000 people would line the harbour to welcome the Pope to Australia.

The Catholic church is the biggest in Australia with about 5 million members, compared to about 4 million Anglicans among the nation's 21 million people.