The pair, in their 20s, became stranded in the 2.5m (8ft) vessel about 200m (665ft) off the Essex coast at 14:30 BST on Monday.
Clacton RNLI said the boat, made from insulation boards, had been "held together with coat-hangers" and glue.
One of the men said it had been "a successful fishing trip" before they had run into trouble.
The 27-year-old, a self-employed builder from Jaywick, said the pair had caught two or three cod and some crabs before they were rescued.
"The boat didn't leak," he said. "I'd do it again."
The men, who were unhurt, were given safety advice and the boat was destroyed.
Volunteer Joff Strutt said the pair had been fishing in the boat all weekend but had run into trouble near Jaywick when the weather turned.
It was "a bit of a project that went a little pear-shaped", Mr Strutt said.
The vessel, built in two days from eight sheets of board, was "not something we've ever seen before", he added.
"[They] are very lucky they were spotted or things could have been a lot worse."
Mr Strutt said it was vital that people only sailed using the correct equipment.
"Neither of the men had lifejackets and one of them couldn't swim," he said.
More on this story from BBC Radio 4's Six O'Clock News.
Two fishermen who went to sea in a homemade boat they built for £9 had to be rescued when their oars broke.