"We see hundreds here and if they remain we have hope...I don't think there is a similar situation like this anywhere else in Greece," said professional diver Vasilis Mentogiannis, an expert in geophysical and underwater surveys who has led efforts to protect searhorses.
Local diver Labros Charelos first spotted the seahorses in the Aitoliko lagoon, in the north part of the Patras Gulf. When the odd seahorse turned into scores he called Mentogiannis.
"It was the first time that I had spotted seahorses and they were in a place I least expected," said Charelos, who adds older fishermen speak of thousands of seahorses decades ago.
Stable populations of seahorses in Greece are unique, said Mentogiannis, who reconstructed an artificial habitat on a barren seabed in north-eastern Greece to save a thriving population there. But numbers there are small compared to Aitoliko, he says, as is the size - some are as tall as 20 centimetres.
Aitoliko resembles a closed lake and reaches a 30 metre depth.