The ordeal had begun to take its toll on the men’s health, prompting the extraordinary rescue by the Kenya Wildlife Service.

Wind had blown masses of the water weed into the boats' paths, blocking their exit.

The invasive plants, native to South America, are believed to have been brought to the East Africa lake by gardeners in about 1980.

They have since undergone explosive growth, expanding far from the shore and then retreating in irregular intervals.

They have caused severe impact to the lake’s fishing industry and even clogged water intakes for a major hydroelectric plant, blacking out entire cities.

But some fishermen say the hyacinth is both a blessing and a curse.

“It will give fish a chance to multiply because overfishing has affected the number of fish in the lake,” Odhiambo Ogengo told the Nairobi Star.

Photo: Sarah Emcc - Flickr