Blue Planet II, the nature documentary produced by the BBC’s Natural History Unit, is in hot water for planting plastic ducks in the sea for a segment on marine pollution. An episode of the popular wildlife show had featured the ducks in the Pacific Ocean near Costa Rica, The Independent reported.

The footage was meant to show how 7,000 plastic toys washed overboard from a ship during a storm in 1992 and are still being found at sea. But viewers alleged on social media that it was not made clear during the programme that the duck toys being displayed had been planted by the filmmakers. They also asked if the plastic ducks had been recovered.

BBC was quick to respond, with the BBC Natural History Unit’s Assistant Producer Rachel Butler saying that the ducks were collected after the filming.

The programme’s producer John Ruthven said on the Blue Planet II blog that filming the re-enactment of the release of the plastic ducks into the sea “was the biggest challenge.” He said the filming crew was “always vigilant to collect every single duck” it had deposited into the sea. “We counted them out and we counted them all back in again,” he added.