The King has expressed his sadness at the "appallingly tragic loss of life" following the MV Barima disaster.
The passenger ferry sank off the coast of Guyana on Saturday evening, with officials confirming on Thursday that the death toll had risen to 72 lives.
Charles, 77, sent a message of condolence to the President of Guyana, Irfaan Ali, who he hosted at Buckingham Palace in January.
"My wife and I were most profoundly shocked and saddened to learn of the appallingly tragic loss of life following the capsizing of the M.V. Barima," the monarch wrote.
© Anadolu via Getty Images"I retain the fondest memories of my visit to your beautiful country, so it is with particular sorrow that I write to convey our deepest possible sympathy and heartfelt condolences to the people of Guyana, and most especially to the families who have lost their loved ones.
"We also pay special tribute to the courage and dedication of the search and rescue teams who continue their efforts under such difficult circumstances. The people of Guyana remain very much in our hearts and our prayers at this time of deep anguish and loss."
In an update issued on Thursday, Guyana's Prime Minister, Mark Phillips, confirmed that of the 72 bodies recovered so far from the disaster, 65 have been positively identified by their families.
He added that the Guyanese government "remains committed to the ongoing rescue and recovery operation" and asked the country to "draw strength from faith, unity and compassion as the nation mourns the lives lost in the MV Barima tragedy".
The King last visited Guyana, located in the northeastern corner of South America, in February 2000 when he was the Prince of Wales.
The King and Queen in Scotland
The monarch's message came as he and his wife, Queen Camilla, played a prominent role at the opening ceremony of the Commonwealth Games in Glasgow on Thursday evening.
Their Majesties emerged from a Tardis, a fictional time machine made famous by British sci-fi series Doctor Who, before taking their seats in the royal box beside the King's youngest son, the Duke of Edinburgh.
© Getty ImagesCharles formally opened the Games in his role as head of the Commonwealth, the ceremonial leader of the association of 56 countries.
He said: "As we gather, we celebrate the dedication and talent of every athlete and team. Your perseverance inspires us, and we eagerly anticipate your achievements in the coming days.
© Getty Images"For these Games, the relay has carried another message – to help remove the plastic pollution that harms our oceans and waterways, and can impact on human health.
"Addressing plastic pollution complements the immense global efforts required to protect 30 per cent of the world's ocean by 2030."
More than 3,000 athletes from 74 nations and territories will compete across 10 sports and six Para sports during the 11-day event.
