The people of Kangiqsujuaq in Canada go to great lengths to add variety to their diet of seal meat, venturing under the sea ice during the extreme low tides of the spring equinox to gather mussels.

It's a race against time. They have less than half an hour to search these temporary caverns before the tide rushes back in. A look-out keeps watch for the returning tide, but warning shouts can't be too loud in case the echoes bring down the ice.