London, England (CNN) -- Britain's Prince William and fiancee Kate Middleton made their first official engagement as a couple Thursday, launching a lifeboat in Wales.
The pair, who are due to marry in April, officially named the "Hereford Endeavour" lifeboat in a ceremony at the Trearddur Bay Lifeboat Station in Anglesey, North Wales.
Middleton, wearing a Vivien Sheriff black-feathered beret, three-quarter length cream coat and suede boots, poured a bottle of champagne over the lifeboat after Prince William made a speech commending the efforts of the volunteers and rescue crew.
"We effectively have two launches today," said CNN royal contributor Mark Saunders. "The launch of the lifeboat by William and Catherine and, at the same time, the launch of William and Catherine into this celebrity saturated world they are going to be living in."
Despite the modest nature of the event, hundreds of people turned out to watch the royal couple conduct their first official duty together.
"In 20 years of royal reporting I've never witnessed quite such excitement for such a single job," said Saunders.
One onlooker told CNN: "It's lovely... I would have thought more people would have brought flowers and things for them but it's lovely... It's low key which is what he (Prince William) wanted."
It's the first public appearance the couple has made since they announced their engagement last November.
"It's a very low-key event, launching a lifeboat on the island where they both live...it's a very good debut event for them," said Saunders.
"They have a very good relationship with the locals here, they are often seen at the local supermarket and buying wine from the local off-license. So for a first event, they couldn't have picked a better one."
The reason for such a low-key ceremony, says Saunders, is to prepare Middleton for life as a royal.
"(The royal family) have learnt many lessons from when Princess Diana first joined the royal family.
"Diana was just thrown in the deep end and absolutely given no guidance whatsoever. They're making sure this time round Catherine is well prepared," he said.
After naming the new Atlantic 85 lifeboat, Prince William and Middleton met members of the charity's lifeboat crew along with fundraising volunteers and were given a demonstration of the vessel's capabilities.
In a statement issued before the ceremony, Lifeboat's Operations Manager, Aubrey Diggle said: "It's an honor to have Prince William and Miss Middleton at our naming ceremony.
"Naming a new lifeboat is always a special occasion for the charity where we can thank our supporters and fundraisers. Having the royal couple there will make the day even more memorable for the whole community."
The couple currently reside in Anglesey while Prince William serves as an RAF search and rescue helicopter pilot.