The stowaways were rescued by the Spanish coastguard in the Canary Islands yesterday, where they were rushed to hospital suffering with severe dehydration.
According to the ship-tracking website Marine Traffic, the men were onboard the oil and chemical tanker Alithini II, which departed from Lagos, Nigeria.
The men, believed to be of sub-Saharan origin, were sighted in their precarious position at the port of Las Palmas, on the Spanish isle Gran Canaria.
Local media Canarias Ahora reported the men had been seeking a better life in Europe.
The photo distributed by Salvamento Maritimo, the maritime safety and rescue society, showed the men exhausted and in desperate need of medical attention.
They were found on the rudder blade, which is outside of the hull of the ship and is usually submerged.
Salvamento Maritimo authorities said on Twitter it was a lucky voyage, considering the extreme exposure to the sea and wind.
Authorities said: “They have been transferred to the port and treated by health services.”
According to Sky News, it is not the first time migrants have tried to stow away on the rudder of a ship.
In October 2020, four people clung to a rudder of an oil tanker from Lagos, hiding for 10 days before Police discovered them on the vessel.
The number of migrants crossing from north Africa to the Canary Islands has spiked since 2019.
Spanish data shows migration by sea to the archipelago increased by 51 per cent in the first five months of this year, compared with a year earlier, reports Reuters.
Despite the apparent dangers, European countries have encountered an influx of migrants entering illegally by sea this year.