A coco de mer seed can weigh up to 25 kilograms - that is heavier than most 7-year-olds. Each one takes around six or seven years to grow on the tree. The shape is unusual too - the seed has two lobes side by side, a bit like the bottom half of a person. Children in Seychelles often giggle when they see one for the first time.
The name 'coco de mer' means 'coconut of the sea' in French. Long before anyone knew where the coco de mer came from, the giant seeds would sometimes wash up on beaches in India and Sri Lanka. Sailors invented all sorts of stories about underwater palm forests. The truth - that they grow on one little island - was only discovered around 250 years ago.
The coco de mer trees grow inside a special forest called the Vall茅e de Mai on Praslin Island. The forest is so important that it is protected as a UNESCO World Heritage Site, which means the whole world has agreed to look after it. Visitors walk along quiet paths under giant palms with leaves the size of beach umbrellas.
Because each seed is so precious and grows so slowly, taking a coco de mer out of Seychelles requires a special government certificate. The country takes very good care of them. Children in Seychelles learn early that this is one of their country's biggest natural treasures.