A German aerospace engineer has celebrated setting a world record for the longest time living under water without depressurisation – 120 days in a submerged capsule off the coast of Panama.

Rudiger Koch, 59, emerged from his 30 sq metre home under the sea on Friday in the presence of Guinness World Records adjudicator Susana Reyes.

She confirmed that Koch had beaten the record previously held by American Joseph Dituri, who spent 100 days living in an underwater lodge in a Florida lagoon.

“It was a great adventure and now it’s over there’s almost a sense of regret actually. I enjoyed my time here very much,” Koch said after leaving the capsule 11 metres under the sea.

“It is beautiful when things calm down and it gets dark and the sea is glowing,” he said of the view through the portholes.

“It is impossible to describe, you have to experience that yourself.”

To celebrate, Koch toasted with champagne and smoked a cigar before leaping into the Caribbean Sea, where a boat picked him up and took him to dry land for a celebratory party.

Koch’s capsule had most of the trappings of modern life: bed, toilet, TV, computer and internet – even an exercise bike.

Located 15 minutes by boat from the coast of northern Panama, it was attached to another chamber perched above the waves by a tube containing a narrow spiral staircase, providing a way down for food and visitors, including a doctor.

Solar panels on the surface provided electricity. There was a backup generator, but no shower.

Koch had told an AFP journalist who visited him halfway through his endeavour that he hoped it would change the way we think about human life – and where we can settle, even permanently.

“What we are trying to do here is prove that the seas are actually a viable environment for human expansion,” he said.

Four cameras filmed his moves in the capsule – capturing his daily life, monitoring his mental health and providing proof that he never came up to the surface.

“We needed witnesses who were monitoring and verifying 24/7 for more than 120 days,” Reyes said.

The record “is undoubtedly one of the most extravagant” and required “a lot of work”, she added.

An admirer of Captain Nemo in Jules Verne’s Twenty Thousand Leagues Under the Sea, Koch kept a copy of the 19th-century sci-fi classic on his bedside table beneath the waves.