You might think it would be easy for a fish to swim between these small islands
But not so
You wouldn't find these little fish in deep water
The open ocean beyond their shallow reef is, in fact, a huge barrier
So how did all these fish come to be here
Colonising new reefs is a challenge faced by fish across the South Pacific but they have a simple solution
Once a year, thousands of groupers gather on the reefs
With the coming of the full moon, an extraordinary event unfoylds
They spawn
A female darts up and releases millions of eggs
quickly followed by the males, who jostle to fertilise them