A dolphin has become stranded after swimming more than five miles inland up a river.
The marine mammal became stuck in the River Parrett in Bridgwater, Somerset, close to the Bristol Channel coastline, Devon and Somerset Fire and Rescue (DSFR) said.
Firefighters launched a rescue effort with the RSPCA after being called shortly after 6pm and urged locals, who have gathered at the scene, not to risk trying to help because of the muddy banks of the river.
They believe the animal is a dolphin or a very similar porpoise.
A DSFR spokesman said: "At this stage it is hoped that with the tide going out that the animal will manage to swim in the right direction back to the sea.
"Police were requested to attend due to the general interest of members of the public.
"The Fire Service are urging people not to try and assist the dolphin/porpoise in any way as they could be putting themselves at risk due to the very muddy conditions on the banks of the River Parrett."