Mola mola (a.k.a the ocean sunfish, and nicknamed by some ‘The Swimming Head’) is the heaviest bony fish in the world, with adults weighing up to 2,000 kilograms. They can measure 3 metres in length and 4 metres from tip to tip. These elusive giants are generally solitary and pelagic, spending much of their time at depth ranging from 200–600 metres. However, for a few months of the year they visit the reefs around Nusa Penida, off the island of Bali, and can be seen coming up from the deep to bask at the surface or getting help from cleaner fish and birds who pick parasites off their skin. There is still little we know about these amazing creatures.