The shooting took place in the town of Puerto Lopez, a popular tourist destination for whale watching, after several men in a van and on motorcycles opened fire on passersby.
The attack is the third in the city this week and a total of nine people have been killed, according to local media.
The shooters are still at large, and according to the police, the attack on the boardwalk appears to be linked to fighting between rival gangs.
Violence has increased in Ecuador in recent years, with shootings in public places not uncommon, and observers say the country appears to be heading for a record murder rate per capita.
