Starting this month, the group will no longer sell activities such as swimming with dolphins, shows involving trained performances and/or any other experiences that require marine animals to leave the water.
Instead, Dertour will fully shift its focus onto "respectful wildlife observation" and supporting conservation efforts through the Dertour Foundation.
It follows a "comprehensive review" carried out in recent months of its animal-related products. "From there, internal discussions evolved into broader conversations with tourism partners and animal welfare experts," said Dertour.
"These exchanges revealed a growing consensus – experiences that involve direct contact with marine mammals or encourage unnatural behaviours no longer align with the values we want to uphold."
Laura Steden, Dertour's director of corporate responsibility, said the group would no longer support attractions "that contradict the natural needs and behaviours of marine animals", including activities "involving direct contact between humans and marine animals" such as swimming with dolphins.
Steden said amendments to Dertour's animal welfare audit and policy had been made with input from animal welfare experts, with whom the group remains "in continuous dialogue".
Dertour, she said, would focus on promoting responsible observation of marine animals in the wild and welfare projects in the destinations it offers, citing its work on elephant welfare in Thailand and Sri Lanka as examples of where it has previously taken action in support of animal welfare.
"We no longer offer activities such as bathing or riding elephants and instead promote responsible observation from a respectful distance," Steden added.
Katheryn Wise, wildlife campaigns manager at World Animal Protection UK, described Dertour's decision as "hugely welcome news".
"With tiny tanks and circus-style tricks, captive whale and dolphin entertainment has no place in the modern world," she said, calling too on Tui Group to follow Dertour's lead. EasyJet holidays and Jet2holidays stopped offering captive cetacean attractions last year.