Manta ray motherships, self-driving eel submarines which can dissolve to avoid enemy detection and fish-shaped torpedoes, are all concept designs imagining the future of underwater warfare.
The series of futuristic submarine designs, which mimic real marine lifeforms, have been created for a Royal Navy project to show how sea defence vessels could look in 50 years' time.
Young British scientists and engineers from UKNEST, a not-for-profit organisation which promotes science, engineering and technology for UK naval design, took part in the design challenge.
A Royal Navy spokesman said: "The UK's brightest and most talented young engineers and scientists came up with the designs after being challenged by the Royal Navy to imagine what a future submarine would look like and how it would be used to keep Britain safe in decades to come."
Commander Peter Pipkin, fleet robotics officer, added: "With more than 70% of the planet's surface covered by water, the oceans remain one of the world's great mysteries and untapped resources.
"It's predicted that in 50 years' time there will be more competition between nations to live and work at sea or under it. So it's with this in mind that the Royal Navy is looking at its future role, and how it will be best equipped to protect Britain's interests around the globe."
"Today's Royal Navy is one of the most technologically advanced forces in the world, and that's because we have always sought to think differently and come up with ideas that challenge traditional thinking.
"If only 10% of these ideas become reality, it will put us at the cutting edge of future warfare and defence operations."
The project, named Nautilus 100, was set up to mark the 100th anniversary of the launch of the USS Nautilus, the world's first nuclear-powered submarine.
Describing the designs, the spokesman said: "The whale shark/manta ray-shaped mothership would be built from super-strong alloys and acrylics, with surfaces which can morph in shape.
"With hybrid algae-electric cruising power and propulsion technologies including tunnel drives which work similarly to a Dyson bladeless fan, the submarine could travel at unprecedented speeds of up to 150 knots.
"This mothership would be capable of launching unmanned underwater vehicles shaped like eels, which carry pods packed with sensors for different missions.
"These pods can damage an enemy vessel, or dissolve on demand at the end of an operation to evade detection."
Rear Admiral Tim Hodgson, the Ministry of Defence's director of submarine capability, said: "We want to encourage our engineers of the future to be bold, think radically and push boundaries.
"From Nelson's tactics at the Battle of Trafalgar to Fisher's revolutionary dreadnought battleships, the Royal Navy's success has always rested on a combination of technology and human skill.
"The pace of global innovation is only going to increase, so for the UK to be a leader in this race it needs to maintain its leadership in skills and technology.
"Hopefully this project has inspired the next generation of British scientists to be bold in their ambitions and I congratulate them for their inspiring work."