An ominousMenacing or threatening. voice speaks over a film of deep water. "There is a creature alive today who has survived millions of years of evolution without change... It will attack and devour anything!"

This is a trailer for the blockbuster 1975 movie Jaws. It tells of an American seaside resort terrorised by a great white shark. Now some experts are predicting that great whites could be coming to British waters.

Britain already has a huge number of sharks: according to some estimates, 10 million small ones and 100,000 larger ones.¹

Many are small and quite harmless. But great whites, which can grow to five metres in length, are a different matter.

In the US they are a growing concern, with five attacks recorded off the Cape Cod peninsulaA piece of land that sticks out from a larger area and is mostly surrounded by water. in the last 12 years - one of them fatal.²

The worry for Britain is that it offers a very similar habitat. An organisation called Ocearch, which tracks shark movements, believes that great whites may now be heading for these shores. 

This is partly because Britain has a lot of seals - over 130,000 according to experts. And seals are a big part of some sharks' diets.

Water temperature is another factor. Though sharks can travel through seas as cold as 2.7C, 16C suits them best - and that is the meanThe mathematical average of two or more numbers. temperature of British waters in summer and autumn. With global warming this is rising, and could become the mean for winter too.

There have actually been reported sightings of great whites off Britain since 1965. But a team which investigated them found that out of 100, only 12 of these were credible - and some might have been sightings of the same shark. 

Experts say that sharks should be more afraid of us than we are of them. More than 100 million are killed around the world each year,⁴ and the population is falling as a result of overfishing, climate change and plastic pollution. 

Should we welcome them?

Yes: Sharks are extraordinary creatures which very rarely attack humans. To see them in the water is a thrilling experience, and the arrival of great whites would add to Britain's biodiversity.

No: Even one person killed by a shark is one too many. If they become a common feature of British waters, people will be afraid to swim in the sea and the economies of coastal resorts will suffer.   

Or... We need to rethink how we see the sea. Great whites have more of a right to be there than we do, since it is their full-time habitat, but we have killed more sharks than sharks have killed humans.

Ominous - Menacing or threatening.

Peninsula - A piece of land that sticks out from a larger area and is mostly surrounded by water.

Mean - The mathematical average of two or more numbers.