Dolphins 'sometimes do come and join us'
20 June 2013 Last updated at 12:40 BST
The beautiful waters of Cardigan Bay on the Welsh coast are a big attraction to tourists, and they're also the summer home of Britain's biggest population of bottlenose dolphins.
But marine scientists are worried that the dolphins are changing their behaviour because of the amount of noise caused by humans.
The BBC's Hywel Griffith spoke with Dafydd Lewis, a skipper in New Quay, Cardigan Bay, about these concerns.