The Deep aquarium powered by Humber tidal power generator
A 150-tonne tidal power vessel is being installed on the Humber to generate electricity for a Hull aquarium.
The Neptune Proteus device, which is 20m (65ft) long and is being installed over three days, will use the tides of the estuary to power The Deep.
It is hoped five additional units will be installed in the future to generate energy for 5,000 homes.
Colin Brown, chief executive of The Deep, said the Humber had "massive" potential as a power source.
"Because of the nature of the aquarium, pumps are running 24/7 - we have a requirement for power all the time - and this one installation is anticipated to provide perhaps 30 or 40 percent of our entire electricity load," said Mr Brown.
"I think in terms of what it can do for the area actually it's much more dramatic.
"We have a tremendous resource here in the Humber. It drains 20 percent of England, it's very tidal and so the potential to use tide generated power in the Humber is massive."
Nigel Petrie, chairman of Neptune Renewable Energy Ltd (NREL), said: "The Humber Estuary's depth and tidal flow makes it one of the best locations in British waters for tidal stream power and it has been identified consistently as a key area for tidal stream power investment."
The project was approved by the government last August.