Tropical islands are an obvious magnet for life

But things are just as busy underwater

Deep currents collide with these islands

Forcing small but vital amounts of nutrients up from the depths

At 50metres deep sea fans are amongst the first to benefit

Closer to the surface corals have sunlight to help them grow

And thanks to the smallest trickle of nutrients

A barren desert can bloom into an underwater oasis

Supporting a greater variety of life than any other ocean habitat

These coral reefs are a magnet for green turtles

Offering a service not available in the open ocean

A good clean-up by a shoal of tangs

This work-over is far from cosmetic

As well as removing parasites

The cleaning stops the build-up of algae

So the turtle can swim freely

But it's also got to feel good