Divers treated to a 'frogfish yawn'

This frogfish was filmed performing a strange routine to warn off divers who approached it off Indonesia.

Known as the 'frogfish yawn' the creatures are able to open their mouths and swallow prey almost twice their size.

But they may not only yawn to catch prey or thwart a potential attack. It could be due to stress, or simply to expel and debris in ingested along with its last meal. Either way, it's an interesting sight.