Since its discovery in 1976, only 17 sightings have been recorded of this elusive fish (3) and the majority of these have been of dead specimens; either accidentally caught or stranded individuals (5). Consequently, very little is known of their natural ecology and behavioural observations have only been possible from the tagging of one individual for a brief two-day period in 1990 (3). This shark was observed to undergo vertical migrations, spending the day in deep water and ascending to midwater at night; it is likely that this migration is undertaken in response to the movements of prey species such as krill (3). Megamouth sharks are thought to feed by swimming through groups of small prey items with their mouths open; however, no direct observations have yet been achieved (3).