Driven by a desire to explore the depths of oceans, the students from the Vič Grammar School built the remotely operated underwater vehicle (ROUV) under the tutelage of their physics teacher.

They performed most of the work and even implemented many of the technological solutions used on their own, but also got some help from several leading Slovenian high-tech companies that have sponsored the project.

The EUR 40,000 craft features a fibreglass external shell designed in the shape of a manta ray, a one-of-a-kind hydraulic propulsion system and a remote navigation system which has been programmed fully by the students.

The hydraulic propulsion system has never been used on an underwater vehicle before, the group boasts on its project website http://calypsoproject.co/en/.

Following a successful test at 10 metres on Tuesday on the Slovenian coast, the students are now setting their sights on achieving their main goal of exploring the bottom of the Dubrovnik Cave at the submarine's maximum depth rating.

Before then the Calypso is slated to have several more test runs, including at the bottom of Slovenia's most famous lake - Bled.

But the group's biggest wish is to eventually explore the world's most famous shipwreck, the Titanic, the physics teacher overseeing the project Rok Capuder has told the STA.

Capuder said projects like Calypso were the "best way for getting youth interested in research and engineering". In addition to allowing students to take charge of their own project, the building of the submarine was also "a lesson in teamwork and exchange of ideas".

The students also worked on fund-raising, as part of which they applied for various grants and contacted a host of potential sponsors. With several expeditions in sight, they are continuing to raise money, including with donations.

"I'm confident that learning from own experience is the best way of teaching," said Capuder, who previously oversaw a project with which students from the school built an atmospheric probe using a helium balloon. The probe reached an altitude of 32 km.