At first glance, this dark shape lurking under the waves in the crystal waters off Hawaii looks like a massive predator.
The ' whale ' has been captured in a stunning photograph in Kailua Bay on the island of Oahu.
But if you look closer, the 'whale' shape is actually just an illusion.
In fact, amazingly it's a huge group of fish swimming together for social reasons, known as a 'shoal'.
A group of fish swimming together
The little fish are said to be 'schooling' together - the term used to describe a group of fish swimming in the same direction.
They are creating the image of a much larger creature.
For scale, the motorboat on the left of the photograph is 12ft long, giving an idea of the size of the massive shoal.