A diver was shocked to discover dozens of dead fish mysteriously scattered across the sea floor of a reef dive site in the Philippines.

Eleuterio Beruan Jr said he had reached approximately 20 metres deep into the ocean before he found the sardinella and goldband fusilier fish across the area in Bohol province on February 25.

Action camera footage shows the diver exploring underwater and picking up some of the fish.

He held one of them and its gut easily disintegrated while some of the fish had holes on their bodies.

Eleuterio said: ‘I found them on the boundary of Anda and Guindulman towns approximately 20 metres deep.'

It was still unclear what caused the fish's death or where they came from, but local officials said they are actively patrolling the area amid speculations that the incident was caused by illegal fishing.

The regional director of the Bureau of Fisheries, Mario Ruinata, said, ‘It is possible that they were fishermen's catch that was harvested late and disposed of in the sea. We are very active in monitoring surveillance and law enforcement.'