During a hearing at Hull Crown Court, Iraqi national Nzar Jabar Mohamad, 33, of Waterloo Street, admitted a charge of conspiring to facilitate illegal immigration.
The investigation relates to an attempt to bring up to 21 people across the channel on a small boat in November 2019. The vessel was purchased for £6,500 and migrants were to be charged up to £10,000 each to make the crossing to the UK.
The probe also examined the use of HGVs travelling across the Channel by ferry to smuggle migrants from Belgium and the Netherlands.
Mohamad (also known as Nazar Masefi) will be sentenced following a further hearing at the same court listed for 2 July.
NCA branch commander Martin Clarke said: “People smuggling, particularly via small boats, is beset with danger but criminals like Mohamad have no regard for the welfare of anyone making these perilous journeys.
“Their sole interest is monetary gain and they view their human cargo as little more than commodities.
“We are determined to do all we can to dismantle the ruthless criminality behind people smuggling, which brings misery to so many individuals.”