The aging revolutionary is suddenly popping up everywhere, most recently at Cuba's National Aquarium on Thursday to take in a dolphin show and chat with aquarium employees, according to a report and photos in the state-run news website Cubadebate.
After four years of near total seclusion, it was the 83-year-old former president's fourth appearance in less than a week.
Photos of Castro's visit to a scientific think tank were published on Saturday. He was interviewed on national television on Monday about his theory that the world is on the brink of a possible nuclear war and he talked to academics at an economics institute on Tuesday.
Thursday's visit to the aquarium in Havana's leafy Miramar neighborhood was a bit lighter, with Castro taking in a dolphin show and asking employees about the internal workings of the center, the website said. He regaled those in attendance with stories about how long he could hold his breath underwater as a youth, two minutes, and reminisced about an opportunity he had to swim with dolphins in Holguin.
Among those who met with the Cuban leader was Celia Guevara March, a veterinarian and the daughter of Ernesto "Che" Guevara, the Argentine revolutionary who fought alongside Castro during the Cuban revolution.
But Castro also turned serious, discussing his theory that a conflict pitting the United States and Israel against Iran would inevitably turn nuclear. He also warned about the threat of environmental disasters and global warming.
"The world lives between two tragedies," Castro told the employees. "War and the environment."
Visits to aquariums by former leaders don't usually prompt world headlines, but Castro has kept largely out of the public eye since undergoing emergency intestinal surgery in July 2006.
The illness forced him to step down, first temporarily and later permanently ,and cede power to his younger brother Raul.
His recovery has been a closely held state secret, and his health has been the subject of persistent rumors among exiles in Florida.
Why the elder Castro has chosen to take a higher profile now is not clear. But despite his sudden visibility, he has so far been careful not to make any comments about goings-on in Cuba, where the government is in the midst of freeing dozens of dissidents.