The drug-carrying vessel was blocked as it made its way towards the Villajoyosa coastline in the Marina Baixa commarca of Alicante province.
At around 3am on Wednesday morning, May 18, the Guardia Civil became suspicious of a boat travelling at 52 knots (96 kmph) off the coast of Villajoyosa (Vila Joiosa) and moved in to intercept it before it reached the mainland.
Once on board the drug carrying vessel, known in Spain as a narcolancha, police discovered around 100 bales of hashish, weighing 3.9 tonnes.
The haul was seized and 10 people aged 22 to 53-years-old were arrested and charged with drug trafficking.
IMAGE: Guardia Civil
The Judicial Police Unit of Alicante, the Maritime Service, the Specialist Group in Underwater Activities and police from Altea and El Campello were also involved in the operation.