A stranded humpback whale known as Timmy was successfully guided onto a transport barge on Tuesday off Germany's Baltic Sea coast, marking a critical milestone in a weeks-long rescue effort that has captivated the country. The whale, which has been stranded for more than a month near the island of Poel in the Wismar Bay area of the state of Mecklenburg-Vorpommern, swam the final stretch into the floating steel enclosure of its own accord after rescuers used ropes and harnesses to manoeuvre him through a specially dredged channel in the sandy seabed. Cheers broke out among onlookers as Timmy entered the barge and blew a fountain of water, prompting emotional scenes among the rescue team, including diver Fred Babbel, who was seen wiping away tears.

The barge — roughly 50 by 13 metres and described as a kind of floating aquarium — will be towed by a tugboat on a multi-day journey of more than 400 kilometres around Denmark and into the North Sea, where, if Timmy is deemed strong enough, he will be released in the hope that he continues on into the Atlantic Ocean, his natural habitat. The operation, funded by two entrepreneurs including Walter Gunz, a co-founder of the electronics retailer MediaMarkt, received exclusive media coverage from the tabloid Bild. Gunz, who said he was unable to watch the moment live and learned of its success from a colleague, was overwhelmed: "I have never prayed so much in my life," he told the German press agency.

Timmy, who weighs approximately 12 tonnes and measures around 10 metres in length, first appeared in the Baltic in early March and repeatedly ran aground. Humpback whales are native to the Atlantic and do not normally enter the Baltic, whose waters are significantly lower in salt content than the ocean the whale likely came from. In the weeks of his stranding, volunteers and emergency services kept Timmy hydrated around the clock using fire hoses, treated blister-like skin lesions with tonnes of zinc ointment, and flew in specialists — including a so-called whale whisperer and a veterinarian — from as far away as Peru and Hawaii.

The rescue has been deeply controversial. Marine scientists at the oceanographic museum in Stralsund and others argued from early on that the whale was critically ill and that the rescue attempt was futile, calling instead for palliative care. Many independent experts continue to warn that the journey itself poses serious risks: the noise of the ship's engines is highly stressful for whales, and the sudden movement could send the animal into shock. Nevertheless, the state's environment minister, Till Backhaus of the centre-left SPD, granted the private initiative permission to proceed and was visibly emotional at the outcome, saying he had wept and had been tempted to jump into the water himself.

Timmy's story has prompted broader reflection in Germany and beyond. Backhaus announced he would bring a proposal to the national environment ministers' conference in early May on how to handle similar situations in future. Marine biologist Fabian Ritter noted that the Netherlands drew important lessons from a similar stranding in 2012, when a humpback whale named Johanna beached on the Dutch coast — an episode Dutch experts say Germany could learn from. Timmy is fitted with a tracker, and his progress will be monitored as rescuers hope he can make the onward journey to the open Atlantic.