Sprinklers on board Britain's biggest and most powerful warship were accidentally set off, sending water cascading into the vessel, the Royal Navy has confirmed.
Video footage captured at the time of the incident shows water spraying downwards from a section of the massive hangar inside the 65,000-tonne HMS Queen Elizabeth.
It is understood the misfiring sprinklers were quickly isolated, the water stopped and cleared - and that some damage was caused in the hangar but not to the rest of the ship.
Believed to have happened on Sunday, it comes weeks after the aircraft carrier was found to have a leaking stern seal, which has now been resolved after repair work.
A Royal Navy spokesman said: "We can confirm that following a routine exercise alongside, the fire warning system was inadvertently triggered on-board HMS Queen Elizabeth and some sprays activated, but she remains on track with her trials programme."
It is understood the sprinklers were activated because of a computer systems glitch and that this is currently being addressed.
The £3.1 billion behemoth is expected to squeeze out of Portsmouth Naval Base between Tuesday and Friday to begin the next leg of her trials - with the start delayed because of the issue.
Set to take place for about a month, the rotary wing trials will involve helicopters taking off from and landing on the four-acre flight deck whilst at sea.
As part of the next batch of tests, the Royal Navy said there is also "an option" for the aircraft carrier to visit the British overseas territory of Gibraltar.
Later this year, the UK's F-35s, the world's most advanced fighter jet, will undertake flight trials from the deck of the aircraft carrier while it is at sea off the east coast of the US.
The UK is currently embarked on a £9.1 billion programme to buy 48 by 2025 of the F-35Bs from American aviation giant Lockheed Martin.
Britain currently has 14 of the warplanes being tested and flown in the US.