A submarine designed to smuggle cocaine on to a Spanish beach was at the centre of a court case today in which seven people face drug-trafficking charges.

The nine-metre submarine, believed to be the first in Europe designed specifically to smuggle drugs, was discovered by police, empty of drugs but with its motor running, afloat off the coast of north-west Spain. The discovery was hailed as signalling the start of a new era of hi-tech, underwater smuggling into Europe, but court evidence suggests it was a fiasco from the start.

The semi-submersible submarine was built by Manuel Clemente, alias The Engineer, in a shed next to his home in the north-western Spanish region of Galicia, according to Spanish prosecutors.

The vessel had room for just one person, who received oxygen from a pipe that stuck up above the surface.

Clemente said he would accompany the submarine to a rendezvous point off the Spanish coast in a yacht, keeping an eye open for police. It was there that the drugs were meant to be transferred from a Colombian boat to the submarine in August 2006.

A Colombian drug cartel had paid €100,000 (£89,000) for the submarine to be built in the hope that it could imitate the success of similar semi-submersibles that are now used to smuggle cocaine into the US.

However, the man hired to pilot the submarine jumped ship when it began to behave erratically on its first mission. A scared Clemente then made sure the submarine was discovered so he could tell the Colombians he had been the victim of a police raid rather than his own incompetence.

Police did not, however, need to be told. They had been tailing Clemente since spotting his submarine during one of its many trips backwards and forwards to the local docks. They arrested him when, in an attempt to pay off his debt to the Colombian cartel, he tried to organise the arrival of a cargo of hashish.

Prosecutors are demanding he be given a 13-year prison sentence.

Drug cartels in Latin America began using semi-submersible boats almost a decade ago. They are built of fibreglass to evade radar and sonar, and the latest designs can carry up to 10 tonnes of drugs and need a crew of four.

Police believe they capture only a fraction of those being used, as crews scuttle them when spotted.

Galicia has been the main entry point of Colombian cocaine into Europe for more than a decade.