The film, La Gran Ola, warns that the mammoth wave will strike the Gulf of Cadiz and wreak havoc on the coast of Huelva and Cadiz, and could kill more than 1,200 people.
There is no pinpoint date for the event, but experts say alarm systems should be put in place to prevent deaths.
The Gulf of Cadiz sits on a major plate boundary posing a huge risk to coastal areas.
Begona Perez, Head of the Division of Oceanography of Spanish Ports, said: “The question is not whether there will be another tsunami, but when will it happen.”
Luis Matias, Researcher of Tectonic and Seismic Risk at the Dom Luiz Institute in Portugal, said: “In the Gulf of Cadiz, several faults could cause an earthquake any time.”
Director of the film, Fernando Arroyo, suggests the Great Lisbon earthquake of 1755, which created a tsunami that killed more than 10,000 people, could be repeated.
“The only reality is that no scientist in the world can claim that it will not be repeated in the short term because there are no indicators in the area,” he said.
“It would affect hundreds of thousands of people and cause very high economic losses.
“For days, large areas could not be evacuated, there would be no electricity, no communications, no water, and entire cities such as Cadiz would have to be evacuated.”
Experts have said systems need to be put in place to prepare for the event.
Mario Lopes, Professor at Technical Superior Institute in Lisbon, said: “Politicians know about the seismic risk and they know it can be reduced, but they do nothing.”