Police claimed they were powerless to stop the beach drop, in Playa de los Alemanes, as a lack of resources meant only one officer was in the area at the time.
Video footage has emerged shocking African migrants being transported into the Spanish territory in North Africa on the back of jet skis.
One onlooker can be heard exclaiming, "what's going on?"
The arrival of the group came after the Spanish Government announced it would take the unprecedented step of closing the crossing between Ceuta and Morocco for the next week to only cars and pedestrians carrying merchandise.
The video may provide a glimpse of changing trends in the routes taken by Mediterranean migrants.
If Spain's average monthly arrivals of between 1,500 and 2,000 people keep up, "it's a pretty good bet that it will overtake Greece", IOM spokesman Joel Millman told The Associated Press.
However, Spain has become an increasingly attractive route for migrants and smugglers this year.
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Over 100,000 migrants reached Europe from North Africa and the Middle East from January to June, the overwhelming majority coming by sea, according to the International Organization of Migration.
Some 11,849 people have arrived in Spain so far this year, compared to 13,246 in all of last year, the IOM says.
According to the IOM, 117,795 refugees entered Europe by sea in 2017 so far, with nearly 83 percent arriving in Italy.
One migrant who had unsuccessfully tried to get to Europe via Libya previous year recently told Reuters that the chaos and violence in that country were leading migrants to consider other routes.
"Often these people go to countries like France or Germany".
But many are desperate to get to mainland Spain, believing that the process in Ceuta is slow or fearing that they will be returned to neighbouring Morocco, and try to hide in lorries boarding ferries.