More than 100 people were on board Cayuco, who overturned when the passengers piled up at one end while a Spanish maritime rescue ship carried assistance.
Emergency services said sudden displacement has dropped many people in the water. Four women and three children died in the incident.
National police, dockers and local diving club members participated in rescue efforts. SUC and Red Cross emergency teams provided medical assistance on site. Two children, both in serious condition, were transported by plane to the hospital for additional care.