Three whales, including a young calf, are free after a close call with a fishing net off Acapulco, Guerrero, on Thursday afternoon.
A 911 call alerted authorities to the situation, and the marines arrived soon after to rescue them.
When a citizen called to report whales trapped off Barra de Coyuca, north of the city center, emergency services forwarded the information to state Civil Protection.
Residents of the area also reported seeing the whales close to the coast, almost in the shorebreak, but said the whales were not trapped.
A boat of marine personnel freed the animals and herded them away from shore. It was the second incident in as many days: on Wednesday, a humpback whale calf was found stranded on the beach in Acapulco, disoriented and dehydrated. Residents threw water on it and later helped authorities push it back into the water despite heavy surf.
Farther south, a whale rescue group has been trained by the International Whaling Commission.
The Assistance Network for Entangled Whales (RABEN) in Huatulco, Oaxaca, includes 20 team members and 40 fishing cooperatives.
Their first job after their training in December was to begin removing illegal fishing nets that could cause whales to become stranded. The team will also track the whales that arrive in Oaxaca to understand their route and destination. Personnel and four boats stand ready to implement Incident Command System (ICS) training to save any whale that becomes stranded as it passes through the area.