Teams there looked after the seals for two months, where they recovered and were taught how to hunt and eat by themselves, rescuers said.
Sue Schwar, founder of South Essex Wildlife Hospital, said: “That’s the whole point of rehabilitating any wild animal is to get it back in the wild as soon as possible.
“As soon as they’re up to weight and there’s no issues, no concerns over their health and feeding… we put them in big plastic kennels, put them in the back of our ambulance, drive them off to a secret location and then open the door and let them go.”
Their release saw them “flopping” into the water before “scampering off”, she said.
Schwar added: “I’m so delighted that they’ve gone off for a good old swim – in a nice way I hope we don’t see them again.”