Fancy a dip?
The River Foss in the centre of York caused passers-by to stop and stare today.
Because it has turned this very striking shade of green.
It was particularly noticeable between Piccadilly and Walmgate. The waters flowing slowly under Foss Bridge were covered in algae.
The river often gets algae on its surface but it is rarely so all-encompassing.
A build-up like this can cause problems. Earlier this year the Environment Agency warned about the dangers of algae forming a ‘bloom’, or scum, on rivers and lakes which can be toxic.
So don’t go in – and don’t let your dog drink from the affected water.