Australian researchers have built what they claim is the world's smallest submarine: a 40cm-long, self-controlling submersible called Serafina.
The tiny submarine, no bigger than a toy, can dive to around 5,000 metres (16,500 feet), turn, somersault and perform a range of scientific tasks.
Its designers say the Serafina could be used in shipwreck recovery, in search and rescue and may have military uses.
The Serafina has a plastic hull, five propellers and rechargeable batteries.
It can travel at the relatively fast underwater speed of one metre per second, equivalent to walking pace, and can hover, tilt and right itself if overturned.
Dr Uwe Zimmer said his department of systems engineering team at Canberra's Australian National University had refined the design so the submersibles could be produced relatively cheaply, starting at about A$1,000 (US$700) each.
Its development and production costs were a tiny fraction of what autonomous submersibles usually cost.
"Being small, for a submersible, is not only a very good thing to have but is actually a very excellent thing," Dr Zimmer said.
"To handle a fully-blown autonomous submersible, you need to have a crane, you need to have a specialised boat, you need to have a calm sea, you need to have a full crew on the sea to operate the vehicle.
"This is a big improvement."
Its designers are concerned the Serafina could be eaten by sea animals
Dr Zimmer added that the Serafina's small size made it much easier to pressurise than larger submersibles.
The only possible problem with the submarine's size, is that it could possibly be eaten by an aquatic creature.
It can be programmed in advance and last on a mission, with its current battery capacity, for up to a day.