MANILA (Reuters) - These colourful jellyfish were caught on camera at a depth of 3,700 metres in waters off South-east Asia.

The luminous creatures, of the Crossota genus, were swimming in the dark waters around the Marianas Trench Marine National Monument, east of the Philippines.

The footage was captured by a remotely operated vehicle, Deep Discoverer, which holds 20 LED lights and nine video cameras.

Researchers are studying mud volcanoes, deep-sea coral and creatures in the region.

But despite decades of study, they say there remain many mysterious and unexplored areas deep underwater.