Moon jellyfish

Hundreds of moon jellies sighted about 350m offshore. Chris Meredith shot some spectacular photos with a Canon G12 compact camera with underwater housing. He did get stung on the face so I wonder whether these were in fact Moon Jellies or another type?! There was a proliferation of jellyfish covering an area of about 20 metres.
The size of the jellyfish in the photo would be about 4.2 cms.