Fish living at Swansea University's school of biological sciences are just yards from the Bristol Channel but they have to have sea water delivered by tanker twice a year.
However, starting later this term, sea water will be delivered direct twice a day through a 5cm- wide, 490m-long pipe that has been tunnelled under the Mumbles Road at a cost of Pounds 60,000.
"It seemed incongruous that with our close proximity to the sea we had to have the sea water delivered," said Andrew Rowley, professor of marine biology.
"So we put in a planning application to start construction on a sunken filter to draw sea water from the foreshore through a pipe. The water can then be pumped straight into our aquarium."
When tunnelling is complete, the fish will enjoy better quality water and the university's biologists will be able to undertake more experiments.
Researcher Susan Shackley said: "It will make our research more competitive at the national and international level as well as improving our facilities for the large number of marine biology students that we teach."