At least 1,100 migrants from Central and South America have disappeared "without a trace" on the Caribbean migrant route since 2020, said Edwin Viales, regional monitor for the IOM Missing Migrants Project.
2022 was the deadliest year on record for Cubans trying to reach the US by sea, with at least 130 migrants perishing in the process, according to the IOM.
At the end of 2022 and start of 2023, home-made rafts were leaving Cuba daily, with videos shared online showing boatpeople cheering each other on at sea.
Little was ever said about those who never arrived at their intended destination.
The group that left from Playa Larga secretly built a raft measuring nine meters (30 feet) from bow to stern, with a sail, eight oars and 10 metal barrels to give buoyancy.
Alvarez's mother said her son kept his departure a secret.
Would-be Cuban migrants often hush up their preparations because emigrating by sea is illegal in Cuba and they do not want their families to worry about them.
'We prayed to God'
Only a few Cubans, like Oniel Machado, a 49-year-old blacksmith from the western city of San Jose de la Lajas, have survived a shipwreck in the Florida Straits to tell the tale.
He and 12 fellow migrants spent hours face down, clinging onto the boards of their raft, which was roiled by a raging sea, one night in April 2022.
"We prayed to God," Machado told AFP a month later, "and we covered ourselves, and when we woke up, we were in US waters."
That journey ended in disappointment for the group, however.
They were picked up by the US Coast Guard and returned to Cuba.