Six men have been found guilty of trying to smuggle Albanian migrants in overcrowded boats across the English Channel.
The operation, which was mainly based in Dymchurch, in Kent, was uncovered following a series of blunders.
Police moved on the gang after they turned to three-person jet skis.
Father and son Leonard and Alfie Powell were convicted at the Old Bailey alongside Wayne Bath, Albert Letchford, Sabah Dulaj and Artur Nutaj.
Another son, George Powell, entered a guilty plea for his part in the conspiracy on 15 May.
Two other men - Alan Viles, 27, from Folkestone, and Francis Wade, 59, from Rochester - were found not guilty.
The nine-week trial heard how one boat linked to the Kent-based gang had to be rescued after nearly sinking.
It was built for six people but had 20 people onboard, including 18 Albanian migrants.
Another boat had to be rescued after it was found travelling the wrong way up a shipping lane, and had run out of fuel.
Had the gang not been stopped by a National Crime Agency-led (NCA) surveillance operation, they would have been the first to have tried to run migrants across the world's busiest shipping route on jet-skis.
NCA senior investigator Mark McCormack raised concerns about the gang's "level of incompetency".
He said: "We have people controlling vessels with no maritime experience, no sailing experience, who have completed very rudimentary courses of one or two days, trying to cross this busy shipping channel at night in a small vessel not utilising lights or radar."
The court heard that migrants, including men, women and children, were charged up to £6,000 each to journey across the Channel from near Calais.
The gang are believed to have carried out one successful trip in a rigid-hulled inflatable boat (RHIB) called Rebel, which was found abandoned on the beach at Dymchurch with children's life jackets on board on 11 May 2016.
When border officials went to investigate, the professed owner, Wayne Bath, claimed to have been out "night fishing" when he experienced engine trouble.
Two weeks later, French police spotted a group of people signalling a boat in the water off Cran d'Escalles beach near Calais.
The migrants began to wade out to meet it, but the Antares RHIB left after a parked car signalled using its headlights.
Prosecutor Timothy Probert-Wood QC told jurors they were "clearly not there for a day on the beach".
Two days later, the gang tried again with the newly acquired White Scanner RHIB, under the watch of NCA agents.
It picked up 18 migrants from France - including two children aged 16 and 17 and a woman - but ran out of fuel on the return journey, forcing the migrants to bale out as the vessel flooded with water.
They were rescued by the coastguard helicopter and RNLI.
White Scanner's two-man crew, Mark Stribling, 35, from Farningham, and Robert Stilwell, 33, from Dartford, were jailed in July 2016.
The gang then bought another larger boat on which the NCA planted a bug to listen to them plotting their next migrant run.
Following a failed attempt on 25 July due to rough seas, the NCA secretly filmed a meeting of the gang after which they bought a jet-ski.
They were arrested before the jet-ski could be brought into use.
All eight defendants had denied conspiring to facilitate a breach of immigration law.
Mr Viles and Mr Wade said they had done favours or jobs for the group, unaware of the people smuggling operation.
Albanian nationals Dulaj and Nutaj acted as "travel agents", finding people who wanted to go to the UK.
Leonard Powell, 66, of Hilltop Farm, Farningham, Alfie Powell, 39, of Button Lane, Swanley, Bath, 38, of Sea Approach, Warden, Letchford, 42, of Rochester Road, Gravesend, Dulaj, 23, of Hospital Way, Catford, south-east London, and Nutaj, 39, of Wheatley Gardens, Edmonton, north London, will be sentenced with George Powell, of Hilltop Farm, Farningham, on 21 September.