This is the description from this commemorative cover
[14 Feb 79] Against a backdrop of skyscrapers, elevated expressways and countless railway loops, the squat ferry wharves of Sydney's Circular Quay no longer hold the charismatic power of the past. However, as the city terminal for commuter ship traffic and weekend boating, the Quay is very much a part of the bustling times, serving one hundred and fifty-two miles of harbour. In 1965, the government modernised the fleet of seventeen ferryboats with hovercraft and sleek hydrofoils. The latest addition to the hydrofoil fleet, and the pride of the Sydney Public Transportation Commission, is the H. V. CURL CURL. With swirling spray and unprecedented speed, Curl Curl slices through the water, making the eleven kilometre trip from Circular Quay to Manly in about fifteen minutes. Curl Curl as modern in design as the multi-shell roof of the four-and-a-half acre Sydney Opera House. A tribute to the technology of the age, the H. V. Curl Curl can carry up to one hundred and forty passengers at a time. With the population of Sydney now at nearly three million people, hydrofoils like Curl Curl are a popular convenience and a boon to the future. Undoubtedly, throughout the 1980s additional hydrofoils will be added to the fleet. As the familiar blue blur of Curl Curl becomes commonplace, Sydney Harbour will continue to grow, and increased use of the hydrofoil promises to bring a second roar of prosperity to Sydney's Circular Quay.