This is the heartwarming moment a team of volunteer divers rescued hundreds of rare fish that had been caught illegally.

The beautifully-coloured parrot fish, bannerfish and marine angelfish were trapped in the iron underwater cage dropped into the Gulf of Thailand.

Divers from the Mu Ko Lanta National Park in Krabi province found the device when they were patrolling the area on August 27.

Each were protected species that trawlers are forced to throw them back into the ocean.

The national park director Weerasak Srisatjang said: "The team were shocked when they saw the large cage under the sea. The immediately released all of the fish.

"There were around one hundred of them in the cage. It is illegal to do this. We need to guard the waters more strictly."

He said the officials are now investigating who built the cruel underwater fish jail in the area.

The team believed that the fish were caught to be sold out in the market illegally. They spent five minutes cutting through the bars to released the fish.

The divers also found a huge fishing net stuck under the water. They believe the net was used by the smugglers who built the cage.

Meanwhile, a resident from a nearby village confessed that customers would often wait for the fish to be dragged ashore then sell them on the black market.

Those who are caught smuggling endangered fish species in Thailand can be imprisoned for up to five years and fined of up to 200,000 Baht (4,800 GBP).