Silverside minnows - which are so small several could fit in the palm of your hand at once - gather just once a year to spawn off the coast of Key Largo, Florida.

Underwater photographer John Chapa, 41, captured the moment the shoal of fish swarmed around a group of divers in aptly named Minnow Caves in the sunshine state.

In some images the stunning view of the coral reef behind the swimmers are obscured by the small critters - which number nearly a million.

The caves are just 20ft underwater and draw vast numbers of these fish once a year.

John, from Miami, said large grouper and nurse sharks sometimes interrupt the tranquil scene for a feeding frenzy.

He said: 'In some cases we've seen grouper so fat and full they lay on the bottom and can't move so they are easy to approach and see up close.'

Luckily for this group of divers there were no predators to interrupt their underwater shoot.

He added: 'When the glass minnows spawn in the summer it is certainly a sight to see.

'It's the only time you're going to see that many minnows in one place. 

(dailymail.co.uk)