Imagine if your favourite beach could power your home.
Out past the break, a large wing under the water flip-flops with the waves, generating electricity. An estuary with turbines below its surface harnesses tidal flows to create power.
Engineers across Europe believe these technologies will be reality and widespread across the world - including Australia - within a decade.
The European Union has poured more than $A150 million into ocean energy research in the past five years.
EU Environment and Maritime Affairs Commissioner Karmenu Vella believes the sector has huge potential to add to the stock of renewable power generation and as an export industry.
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"The potential is so big that when we talk for example about wave energy, if we take 0.1 per cent of the energy in waves, we could supply the global demand for power five times over," he told AAP in Brussels.
"In Europe, we think that through ocean energy we could supply some 10 per cent at least of the renewable demands in the EU."
While the technology is still being developed, it's anticipated it will take a lot less time to become commercially viable than wind and solar.
There are several projects now in the proof-of-concept or long-term testing phases, such as a WaveRoller plant, operated by Finnish company AW Energy, that Mr Vella recently visited off the coast of Portugal.
A range of other technologies is being tested around the Orkney Islands north of Scotland.
"They are no longer on paper ... It's not something that we will be seeing in the future, this is something that is already there," Mr Vella said.
AW Energy has highlighted Australia's well-populated east coast as a prime location for wave energy power plants.
One of the advantages of harnessing the ocean's power is tidal and wave movements are always there - unlike wind or sunshine - making it more reliable and complementary to other intermittent forms of renewable energy.
And because the machines are largely underwater, they have a lower visual impact than wind turbines or other onshore power plants.
The writer, Katina Curtis, is taking part in an EU-sponsored study tour.
