The 10-metre-long rubber boats were found at the Suffolk port on Saturday after arriving in a container from China.
National Crime Agency (NCA) and Border Force officers confiscated the haul, thought to be the first time a bulk consignment of boats and engines has been intercepted in the UK.
The contents of the container were about to be shipped on to Hamburg, where investigators believe it would have been offloaded.
Germany is a well-known staging post for equipment used by people smugglers in northern France and Belgium, according to the NCA.
The NCA said each boat could have carried about 80 people, meaning they could have potentially transported 2,000 people towards the UK if they had got through to the beaches.
Branch commander Adam Berry said the seizure would have “put a huge dent” in the profits of the people-smuggling gangs.
“It will also have stopped these dangerous boats and under-powered engines being used to put lives at risk in the Channel,” Mr Berry added.
“Once we identified that the shipment would pass through a UK port on its way to Germany, we were able to work quickly with our partners at Border Force to ensure it would go no further.”
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Border Security commander Duncan Capps said “disruptions like these to criminal networks and their supply lines are happening more than ever before”.
More than 1,500 boats and engines have been seized by the NCA and its international partners since early 2023 – when it started targeting supply chains.
Over 100 investigations are also ongoing into individuals or networks involved in people smuggling.
Since Labour’s election victory in July 2024, some 77,183 migrants have arrived in the UK after crossing the Channel during Sir Keir Starmer’s premiership, according to analysis by the Press Association of government data.
Home Office figures show 12,469 arrivals have been recorded so far this year.
This is 47% lower than the number recorded by this time last year and down 21% on the same period in 2024.
