Built by researchers at Canberra's Australian National University, Serafina has the potential of performing an endless range of tasks - from shipwreck recovery to mineral exploration and search and rescue missions.

Cheap and with the capability of diving 16,500m, it may do for submersible craft what remote-controlled model-sized aircraft are already doing for advanced military powers.

Or it may simply be a toy, the team says.

The Serafina has five propellers and a plastic hull, crammed with rechargeable batteries and circuitry.

Significant agility

It can travel at the relatively fast underwater speed of one metre a second, equivalent to walking pace, and can hover, tilt and right itself if overturned.

Team leader Uwe Zimmer said his department of systems engineering team had refined the design so Serafina could be produced relatively cheaply, starting at about $1000 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," Zimmer said.

"When I offer companies and research institutions the possibility of having submersibles they can just throw overboard and fish out of the water later on, this is a big improvement.

"The reason why small is beautiful in this case is that, if you are small enough, the pressurisation for the deep sea becomes significantly more easy," Zimmer added.

The only problem could be that it being very small, Serafina could be eaten by an aquatic creature.