In a now-viral video shared on Instagram by hrhprincgeorge- a popular fan account for Prince George and the British royal family - Prince William can be seen smiling to himself, seemingly holding back laughter, while others around him sit somberly or read what appears to be a program.
The visit is their first trip overseas as a married couple, following their wedding in May.
As an Honorary Air Commandant of the RAF Air Cadets, the Duchess of Cambridge has added her sparkling Air Cadets Dacre brooch to her lapel.
The Duke and Duchess of Sussex have touched down in Dublin for their two-day visit having coming straight from Kensington Palace where they celebrated 100 years of the RAF.
They will also visit the Book of Kells as well as Guinness Storehouse and the Dáil.
The Duke and Duchess will also have a moment for reflection at the Famine Memorial, before visiting EPIC, the Irish Emigration Museum, telling the story of the 10 million Irish people who have emigrated across the world.
Kevin Doyle, political editor at the Irish Independent, tweeted that he hadn't been able to confirm whether Harry and Meghan drank "any of the 14 bottles of water".
The couple attended a garden party at the British Ambassador's residence at Glencairn.